It’s full of plot holes. Don’t do it.
I think that Emma & infant Henry living out of her car is certainly a possibility, but Henry would be too young to remember. As far as I know, he doesn’t know his parents lived out of the car, either. And in the NY year, he had “memories” of growing up w Emma so no grand Q&A session there, either. We did have the scene in SB after she got kicked out of Granny’s, but I don’t recall Henry being privy to that.
I mean, if my Mom couldn’t stay wherever she was living, “sleeping in her car” is just not the first assumption I would make. Add that onto a scene that had no real “point” in the episode, and it makes it doubly suspicious. The only reason that scene existed was for Henry to allude to his parents’ history, by making assumptions that – while historically accurate – he had no logical reason to make. I’m gonna call Shenanigans on that one.
Cause this story needs some mending & a better happy ending...