Tony Stark knew the tesseract and Pym were in the NJ Shield base because Howard told him about meeting Tony there. It would have happened at some point right before the death of the Starks, as Tony needed to look like his older self. Howard probably told it as an oddity, not realizing it was actually Tony.
Ironman tells Cap something like - I know that I know, but I can’t tell you how I know - as if he suddenly put it all together there in 2013. This keeps Cap within the same timeline when he stays.
Tony Stark knew the tesseract and Pym were in the NJ Shield base because Howard told him about meeting Tony there. It would have happened at some point right before the death of the Starks, as Tony needed to look like his older self. Howard probably told it as an oddity, not realizing it was actually Tony.
Ironman tells Cap something like - I know that I know, but I can’t tell you how I know - as if he suddenly put it all together there in 2013. This keeps Cap within the same timeline when he stays.
Cool idea. Unfortunately, I don’t see how that would work, since Endgame uses branching-paths time travel instead of closed-loop.
Except HTF did Cap show back up at the end? Did he take another pym* particle jump back to give the shield to Falcon?
That seems to be the official line from the Russos and/or Kevin Feige, yes. Take that however you will.