I think even reddit is not arrogant enough to attempt that. It would require removing every moderator from every subreddit that has gone private at the same time.

Even if reddit forces subreddit's public, the auto-mod script to remove all new comments and posts is 2 lines of YAML. Having a public site with a bunch of upset and unaccountable mods is only inviting them to become bad actors and actively sabotage the site, which will do much much more damage than going private