Our lack of understanding fits given that the Thargoids are a completely alien species that we cannot in general communicate with and that are knowledge comes from a different extinct alien species whose records relating to the Thargoids might be reliable or might turn out to be from archives of the equivalent of a redtop newspaper.
I'm not saying it's wrong that there are mysteries left in that story, but they're somewhat pointless if it's not being continued. Which it has not been the last six(ish) months. I'd go as far as to argue there has not really been much of any story development since August-October 2023/3309, except for when the Thargoids hit Shinrarta for an unknown reason, then went to Sol with their Titan.
... I don't consider the Guardian records a reliable source. Too much "History written by the victor", not enough concrete details about how it all actually happened. Whether those were simply lost or deliberately being omitted is up for debate.
Pretty sure Thargoids being able to communicate just fine and just actively choosing not to because they are rampant xenophobes has been the lore for Elite Dangerous since the novels came out.
And humans have been? Replace "Thargoids" with "humans" in that sentence and it would be just as accurate. If not more accurate because while the Thargoids were showing restraint and only destroying ships stealing their stuff* (or carrying Guardian relics which could and have been weaponized to various extents), we began blasting them indiscriminately for them daring to have a problem another belligerent species was taking their stuff and killing them unprovoked, in their own territory. Older FFE lore (which I believe is referenced here and there in the game as well) even suggests it was humans recklessly destroying a Thargoid ship merely observing them, that kicked things off back then.
*Exception made to meta-alloys. They will "ask" politely for those at first and glow green, then deploy a Thargon swarm and go red if you don't, but otherwise leave you alone after some time, if you insist on keeping them anyway.
If what you say the novels suggest is accurate, it certainly stands in stark opposition to things and contexts shown more or less subtly in the game itself. I did not see the Thargoids make a giant weapon of extermination yet... or attempt a full wipeout despite said weapon we threw in their face.