ED focused on a MVP first, and after that started expanding the game towards David Braben's full vision. This is a valid way, because you can present a full release earlier. But it also has its drawbacks, because every time you introduce a new expansion with new features, you must rewrite plenty of things from the ground up. This can lead up to long times between expansions, and people thinking the game lacks content, because they dont understand that they are not really playing the full game.
SC has chosen a different path, to focus directly on the full vision, including every feature. This is good because you do things once and you don't have to rewrite so much stuff each time you do an expansion.
That is absolutely false in every sense. When things are properly scoped out from the beginning, nothing needs to be rewritten or restructured as it was already prepared for in the beginning. Kind of like the whole "space" not really being there and using triggers to make it seem like a space suit is needed in SC. That will require massive changes if they intend to make it so '90s style shortcuts and triggers don't cut it anymore - like if they want to account for dynamic decompression zones.
However, when properly designing and saying "at some point I would like this, but we can't do it now" it can still be prepared for and designed so that it can implemented with the only changes being some new GUI entries or displays, some new menu items, or whatever is needed to introduce the feature but not massive rewrites as you suggest. The only reason that would happen is due to lack of vision, lack of a real road map, and complete mismanagement like what CR is doing.
The Alpha 3.0 demo was also just that, designed specifically to demo off for the "cool wow" and get more donations. It was very carefully designed, scripted, and configured so that it played exactly how they wanted it to. Like when the player KNEW there would be a pirate waiting in the door way. Then there is one scene where the player is very clearly not being controlled, he just glides down stairs, and the scenes where he is doing a scenic walk through moving along and focusing on specific objects as the character passes then it switches back to player control. The public demos have all been designed for one thing: to sell more ships. They aren't an example of the playable game. Still over a year and that pupil to planet doesn't exist on anyone's client, because it was carefully rendered and prepared - it wasn't playable. The whole thing has been smoke and mirrors to get more money and putting out a terrible bug ridden tech demo that is janky and incredibly limited. They don't even have Double Precision Floating Point in it yet, the game is still limited to a single two bases and a few planets - none of which can be flown to despite it being demoed a year ago - there are actual boundaries/map limits, and it isn't even a complete single system yet. And somehow they are going to have 100 of these next year? They can't even get one done in 2 years. Plus CR constantly diverts duties so that he can put together these fundraising demos to show off, which don't actually feed back into how the game will play so it is wasted time, and it is Freelancer all over again.