Remember the Dreaded Third Option I mentioned when we were speculating about the Super Mutants?
Apparently they were made by the Institute.
https://www.reddit.com/r/falloutlore/comments/3spc0j/spoiler_fallout_4_super_mutants/
Ugh, I hate this 'everyone and their grandma has access to FEV' bullshit.
Vault-tec in FOBOS was already a stretch for having access to it and doing research on improving it. All those who actually played the game (I know, painful) might recall that FEV was not even mentioned in the game itself, rather Vault-tec was researching a cure for mutation induced sterility.
But in Fallout 3 we go a Vault that was doing FEV research, despite that FEV only existed for roughly a year, and Mariposa base was specifically re purposed for the purpose of studying FEV and its effects and use, and that the 'proto super mutants' (I think there were already human experiments before the war happened) and the actually super mutants were created by the Master here.
The idea that the MIT/CIT would get access to FEV is a real stretch as FEV was a West Tek/government research project. That they might have recruited some outside researchers/scientists to help them work on the genetics work is not a stretch but I doubt that West Tek's leadership would sent samples to the Institute, especially after all the Chinese espionage problems.
I honestly hate these retcons about Jet, Super Mutants, Power Armor (only the pre T-51b ones used energy cells that were quickly exhausted), continuous changes in what the Vaults were about.
Fallout 3 and 4 are really not the successors to Fallout 1 and 2, it is almost like the new Battlestar Galactica series and Star Trek movies; Fallout in name only 'FINO'.
Elements and names are there but that is it.