OP here - (in my story) the Teams account creator did not do this out of cruelty, they just didn't know this is what Dropbox does. I imagine very few people realize that this is how it works.
What should've happened is this: revoke my access to the team folder and downgrade my account back to Free. (Then, annoy me and refuse to sync until I go down to 2GB of usage.) That would be good design.