They are buddies.
Overeem actually injured Jon Jones in sparring when they trained at Winkeljon. And he felt awful. Jones had to cancel his fight he got so messed up. I think it was the reason the first DC fight was pushed back. Apparently they were just warming up to and Reem fell on his knee and injured it.
"And I felt terrible man, because I was looking forward to that fight. Of course obviously [Jones]’s had a great career, he’s a great athlete, but I also like him as a friend. So, you never want to do that to your buddies that are your teammates, because you feel terrible." - Overeem
From mma fighting article back in the day.
https://www.mmafighting.com/2014/9/...em-on-injuring-jon-jones-in-sparring-mma-news
Plus no one in their right mind would actually want to fight Overeem. There is a reason virtually no one calls him out. You may win, But chances are hes gonna hurt you bad. Dude is a monster. Jon is not that stupid.