As a manager in a company with an in-office policy which I don’t like - I will tow the policy line if I’m asked in an official capacity, otherwise it’s my ass. But if my DRs shirk the policy then the only reason I’ll take action is if HR catches on (they do occasionally look at data from the building access logs), or if it causes waves in the team.

It’s also possible (I’d say - likely) that your boss knew, and had no desire to do anything about it.