I'm having the same issue. Im trying to switch to 3-4 defense and 4-3 is still showing up!
I think I just figured it out. It literally doesn't matter what playbook you have equipped. The game simply goes off of the playbooks you have set in your main settings. I like to use the spread playbook, and I can't find it and have no clue how to get it, but I'm currently using the spread playbook because that's what I have set to in the settings.
tldr no matter what team you play for and what playbook you have selected in MUT, change your settings to whichever playbooks you want and they'll show up in game.
