I have been thinking about this one (and actually a bunch of other similar BS tropes) recently.. I have remembered a bunch of times people in real life have taken these tropes in as "life rules" and started to behave by them after seeing these on tv or movies. It is really, really weird. Not just this dating thing, but like anything from wearing same or even just similar clothes for two days in row, that's no way an issue in real life with sane people. But some people see a character react that way in a made-up tv show and suddenly start repeating it in real life?

I agree completely. If that happens in real life, it should be a huge fucking red flag.

Yeah, "retroactive jealousy" is a very dumb trope that should seldom if ever be used in a story, IMO. Tropes aren't inherently bad, most stories are full of them. But some of them are weak sauce, and this is one of them. I tried to find an entry for it on tvropes.org and couldn't find one, which is surprising. It's a fairly common trope, and they have a lot of jealousy-themed tropes in their database. Could be a skill issue on my part and I just didn't find it.

Yeah, that's one of the idiot plot tools that bothers me too. It happens in real life, but hopefully not in people who have entered adulthood.

Not wanting to hear about it? That's fine.
Irrational feelings of retroactive possessiveness or jealousy? Also fine.
Wanting some relationship reassurance? Also totally fine.

The key part is being mature and recognizing that it's about your needs, and not the other person's behavior. Being upset with someone else because of the above is unreasonable. Letting them know you'd like a reassurance isn't.

People be silly sometimes though.

I honestly don't recall ever seeing this trope but its likely in shows and I just gloss over it.