Ah multiverse theory then.... all lore is valid just depends which universe you are in.... ;-)
On a slightly more serious note... the only menton of using previous games to enrich Elite Dangerous I have seen/heard/read from FD was from FFE (pretty sure it was that one rather than Elite II) in one fo the Dev Diaries by MB when he was talking about how they created the Galaxy. They imported some of the more "important" parts of the Galaxy (i.e. the old worlds, key systems of importance) from the old game and they hand crafted a few systems too (Sol being one).
However even with importing in that data they had to change things about... pretty sure the old worlds (Lave included) are actually in a different part of the Milkyway as it didn't fit with the new galaxy in Elite Dangerous.
EDIT:
Here's a link to the video and summary I made earlier ;-)
(Oh and it was Achenar that moved not the old worlds... bad memory! but "The space occupied by the systems from FFE is much larger in Elite Dangerous as they moved a lot of them around")
Can't stop thinking. We have exact date in codex when RAXXLA was known. At that time it was only 5-6 major systems colonized + hyper drive was expensive so could be used only by goverments/corporations. So that should be somewhere dumb close. I even had idea toast describes tattoo on NPC's head...
forums.frontier.co.uk
And some interesting points I made at the time too... 
"
- There were two main goals... model the galaxy a closely as possible to the milky way and for the game to continue on from where FFE left off (3250) - game continues in 3300
- They started with the Gliese & Hipparcos catalogues to provide the bulk of the data in the immediate region and major stars out to 600 - 700 LY (Database of about 75,000 stars)
- Then they brought "stuff" across from Frontier First Ecounters ("Favourite places people like to visit and there's also some key locations from.... erm... eh... the fiction background that we've been putting together, so a good example of that is Lave of course which is famous from the very first game. So what we've been putting together is a series of overrides. So the galaxy itself is constructed from an algorithm so we basically have a number of complex equations that say that there should be a star here it;s in a spiral arm, that kind of thing and that then generates the whole galaxy but what we then have is a manual list of overrides that say actually there is a star at this specific point here, its of this type, we can assign the planets and the moons also as overrides within the system. So that means that some systems, the solar system being the classic example will be fully sort of manually set up so everything that you see is familiar to you. Where with other systems we'll let the system generate what star it is and the planets but we might say that particular planet there needs to be an earth type planet. So a lot of that information we've extracted from FFE and that's been compiled into a big database that can then be blended into the game data.")
- Then they added in the backer's naming promise for stars and planets (they tried to match the descriptions provided by backers to potential systems).
- Matching systems was also an interesting task when bringing data across from FFE as there were a number of stars in FFE that they had to relocate to match real star positions. So the map from FFE has changed quite a bit, but there's still the familiar layout that Achenar is down below the solar system but the positions are more accurate but makes space feel that much bigger.
- Then they planned to implement what's changed since 2250 - whether disputed systems are still disputed, are there any new colonies
- "There's legends, ...erm that need to be tracked down" 8:03
Some interesting points....
- At the point of recording they had done most of the placing of "Stuff" and were just deciding on changes since FFE.
- The totally hand crafted solar system is still broken.... or is it? ;-)
- The fiction bits of the galaxy are based on FFE and not Elite '84 (I've done checks on lists of systems and planets from the original game but not considered FFE before as I didn't play it)
- They took the time to place specific planets in specific systems as they hand crafted more than just Sol.
- The space occupied by the systems from FFE is much larger in Elite Dangerous as they moved a lot of them around
- If you're looking for the least retconned previous game then it's FFE? (Although Raxxla was never mentioned in FFE)
- And my favourite.... "There's legends, ....erm that need to be tracked down" 8:03"
EDIT OVER!
I would however say that in my humble opinion there is a bit of lore that has been added in over the years that has come from the previous games and pretty sure some of Galnet stories early on were lifted from previous games and slightly modified, but even that is quite a while ago now so examples elude me...
Whilst I don't disagree with your views (as I always say anyone's idea is just as valid as someone else's until someone finds Raxxla!).... There is a part of me that is split on whether to find Raxxla it would be cool to have to know the lore of all current and previous sources, be able to decypher which bits are still valid which have been retconned whilst at the same time being able to make sense of all the discrepancies and re-writes/reboots over the years within the game and all the ancilliary products (books, RPG, etc) or whether that would give me a massive sense of humour failure.... LOL
The way I personally approach it is that Elite Dangerous and anything mentioned in it is gospel (whether it's subterfuge or not).... Anything else is a guide and most likely not valid lore unless it comes from someone involved in the current game in someway but I don't rule it out completely...
e.g. Thargoids were not in the game... they were conspicuously not mentioned by FD early on with the usual "we have nothing to announce at this time" type answers and then they appeared in the game and parts of the old law came in to force with the 1st Thargoid war.... but some details have changed/retconned/rebooted....
but always remember "in the land of the blind, the one-eyed man is king" so you may well be right ;-)