And for the proof: You can see the before and after I disabled it:
I had been having a lot of crashes in 4.17 when hitting Compile, and had this crazy increase in BP Compile times, luckily found an AnswerHub post, which hasn’t been addressed by Epic: Slow compiling of BPs in 4.17.2? - Blueprint - Unreal Engine Forums
Definitely a serious issue.
Are you by any chance using some plugin that could need custom compilation? blueprint compilation manager has broken those too but epic is going to review them on 4.19. Maybe it’s not the same bug, but just so you have that information
It’s an interesting theory, and probably right, that plugins are affecting the compilation manager. But, it should definitely have been taking those into account from the start.