Pics with Ex

For context my partner and I are in a monogam-ish relationship where we just chat/trade with others and look for thirds. We’re both on grindr and sniffies. My partner showed me some chats and of course nudes were sent (which is completely fine). Something the kind of bothered me was that my partner was sendings pics of them having sex with their ex. I can get why my partner send it because they did look good in it, but the fact that it’s with their ex I find kind of weird. What are y’alls thoughts if you found yourself in this situation?