1. UA made this clear at the time it extended status that OP would not receive freebie Plus Points if he did not earn them.
2. UA did not "clawback" anything. OP did not earn them, either in the practical sense or the terms UA published.
It is also entirely appropriate. It was fine to extend status due to the pandemic. But, people who were not flying were not spending their PlusPoints, so no reason to grant them anyway.