Short answer is: At the same time with one account? No.
It is much more about using separate accounts rather than how you get a license. If you have an "EA" copy and your son has one through Game Pass, WITH separate accounts, you are good!
Hope that makes sense / helps!
From what I can tell, Battlefield 6 will likely not be on game pass. So I would like to know the answer to the OP's question with the caveat that it doesn't require 2 copies to be played at the same time.
I don't have an Xbox, but I have a buddy that has both an Xbox and a PC and it would be nice if he didn't have to purchase 2 copies if he wanted to switch over to his Xbox or something.
