Boyfriend still friends with his old fuck buddy?

My boyfriend is still friends with his old fuck buddy. They slept on/off for over a year and only a few weeks before we met. Last week he was supposed to call, but couldn't because he was in the hospital. In my own horrible manner, I looked at his phone this morning to see that he had called her chatted about an hour and then texted her telling how much he appreciates and values her for always being understanding and there for him. He says he never has had any feelings for her. She has sent him postcards, painted paintings for him.
It seems like an odd relationship. Or is it just me because I don't believe you can be platonic with old fuck buddies? He has never introduced me to her either which seems strange if it's just friendly. Can you be just great friends with someone you used to sleep with so much?
Boyfriend still friends with his old fuck buddy?
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