Supervisor and Postmaster Both Carried a Route Today

As the title says, we were extremely short staffed. Record number of callouts that I've seen since I started (6 months ago). We had a total of 9 uncovered routes (out of 24), not including relay routes. So our PM and 1 supe each did an entire route today.

I understand this is against the rules, but I'm a relatively new cca and I've heard whispers of a grievance being filed with the union. What does that mean? What happens? Also were there any alternatives? I think we called other officers to see if they could lend anyone and were still very short. I cased an extra route to be pivoted and didn't start my walking route until 11:30-11:45. How is this supposed to work in these crazy instances?