I think it's because Spencer has a long track record of doing the opposite with his opponents so for it to happen with a teammate was just weird.
Spencer clearly didn't want to wrestle that match for a variety of reasons (injury risk, he was clearly pretty worn out after the semis and the match doesn't even count), he was told he needed to if Drake wanted it (which he did) I think Spencer also took offense to it because in many ways, that implied Drake thought he could outright beat him (why else do you want a match?)
He had a "You like that?" moment and that's all there is to it. Drake's family didn't appreciate it so they've since leaked he doesn't practice with the team.
Candidly, I don't think Spencer is all that interested in taking a mentoring role with the young guys. I don't blame him either, I think the last few years has been mentally and physically draining on him. The fact he is in college a 6th year and hasn't wrestled an international free event in college has to annoy him a bit. If he isn't in the room even then that definitely reinforces it. Kemerer, DeSanto, Eierman, Marinelli were his guys and he wanted to finish up with them (with a title of course) Now he wants #4 and to get out.