My (35f) fiancé (34m) can’t let go on social media

Given social media and accessibility my gut says this is a red flag I should walk away from where my (35f) fiance (34m) loves to follow and chat with random women online via his personal or now second (private) instagram account?

While I know he’s not doing anything directly wrong like meeting up or exchanging numbers his need to keep tabs on exs he’s dated or women he’s previously spoken too before we met seems immature and not ready for the next step of life.

I had to explain that even following and liking posts sends the wrong signal. It looks disrespectful to our relationship. For clarity some are just bikini influencers but some are actual girls in our hometown who just post random photos looking for validation from the internet.

This feels like I’m ignoring a red flag of someone who isn’t ready to settle down or it’s really NTBD and just how people use social media.