Perhaps Google just wanted to scare businesses on the legacy plan into migrating to the paid service, expecting that those who could afford to pay wouldn't leave it to the last minute.
I think they're pretty justified to block additional uploads for any over their stated (but poorly enforced) quota, and give a window for users to get back under quota then just delete it for the obvious bad actors.
G Suite legacy accounts have always been limited to 15GB, and my newsletter inbox has been barred once from receiving further email because I'm always close to the limit.
Given how long it took and their original apathy to the negative reaction, I’m guessing a large percentage of users were migrating away rather than paying to upgrade.