Friends after long distance relationship

Hello everyone,

I need opinions on this. Boyfriend has had some rocky relationships (been cheated on etc) so he does find it difficult to open up and trust.

A previous ex, he had a very long distance relationship with, ended in 2017 with her ignoring him essentially cause it wasn't working anymore. They were friends after this though, even through his last relationship.

She tried to distance themselves though, and I have reason to believe it's because she got engaged and then married (don't think he knows this). But she still messages him to 'check up on him'. Asking how he's doing etc. About 4 months into our relationship he called her out on it, saying it was confusing whenever she wanted to put some space between them, this lead to him saying that he missed her, he's thinks about her everyday but he doesn't want to be a footnote in her life. Since then they barely message, it's now 8 months later.

Can you miss and think about a previous partner as a friend? Because that's what he told me, that it was all platonic but I'm not so sure.

Thank you