Found this possible solution in the github issue
(Credit to CrazyCSIW6)
Edit: Figured it out. PRIVATE MATCH is what's forcing pro perks.
Setting xblive_privatematch to 0 will fix the problem, even if the server is already running.
Edit 2: This isn't working properly, the game now thinks there's no teams unless players join with privatematch set to 1
Edit 3: Bandaid solution. Join game, pick class, spawn bots, set privatematch to 0, pick a different class. Problem solved.
This seemed to work, but is there a better/ more permanent solution to this? Maybe a way to modify the GSC?