Xbox Player connected to PC Server

So after a while of testing one of my games, we finally realized that one of the testers who was testing on Xbox somehow was playing with the rest of us in a PC server. Now, I don’t remember PC players being able to play with Xbox players, but i’m pretty sure they can’t.

We tried many tests to replicate the situation, and we think we figured it out. The only way that worked for us is if you press the “play” button for the same game on Xbox & on the site at the same time. Then it will indeed put your Xbox player into a PC server. However, he was friends with me. Don’t know if that has anything to do with it.