This is a weird rule for people uploading videos. You can't just decide to show ads on your videos. Youtube requires you to meet certain guidelines. The last time I checked you need 4,000+ hours of view time each year and 1,000+ subscribers to be allowed to show ads on your videos. That means smaller channels who have limited audiences would have no way to avoid termination because Youtube is blocking themselves from…
It's very likely that if the said small channels are indeed too small to be allowed to monetize, then they would fall under the not profitable accounts even if they were allowed to monetize.
It might take 6 months or even a year+ of dedicated uploading to meet those guidelines for most content (unless it's a really popular / trending niche like a new game, etc.).
If Youtube starts banning those accounts then they are effectively not allowing anyone else to join their platform because they would be terminated before they have a chance to get popular enough to enable ads so that Youtube can make money.