That study wants to shed some light on whether UBI is viable or not, but limits UBI for two years. I suppose people are then less inclined to change anything in there life and just see UBI as a nice, not-life-changing win in the lottery. People are not behaving as with a "real" UBI. Can we agree on that?

There is some aspect of this kind of experiment/study to find out how individuals would perform if they didn't have the guaranteed income in the past but then suddenly do, but that's only meaningful for the transitional generation.

IMHO you can't ignore this that easily. When more people are quitting their jobs or switch to part-time jobs from full-time jobs due to UBI, the government loses taxes but now needs to pay for UBI. This is super-important to see if this whole thing is financially feasible.

IIUC you are arguing that people that grew up with UBI would behave differently compared to people that just switched to UBI? To be honest I don't feel this particular convincing, why should this be the case? There probably isn't any data on it either. Even if it would, the government/state still has to get through the transition period. One could with the same right claim that future generations are less inclined to work/educate than the transitional generation and thus make financing UBI even more difficult.