This is my experience. All my guy friends growing up were totally willing to both open up on a personal level when it was just me and them.
However, too many of them were willing to make too many jokes at my expense when in a group of multiple guys. So they weren't super helpful in keeping me as that person. I'm sure i was a bit more "thin skinned" or whatever than I should be been, but I expected more from them, since they were willing to be so sincere when it's just me and them. The tonal whiplash was too hard to take.
Hopefully we've all grown a bit since then.