After re-reading this thread, I’d like to add more to my response above regarding whether or not a NRLCA District Representative would tell a carrier they could walk out of a PDI:
I’m thinking a DR might have said something like “You can do whatever you want, go ahead and get up and walk out of the PDI, but you can be disciplined for that.” And the OP conveniently didn’t hear that last bit.
It’s kind of like the response stewards generally give when asked, “Can I grieve <whatever >?” and the response is, “Yes, you can grieve the sky being blue or the grass green. Doesn’t mean you will prevail in that grievance.” Or “Do I have to follow a direct order?” and the response is “You don’t have to do anything but understand that you could face discipline for failing to follow.”
I’m reminded once again in reading OP’s comments that what a steward says, what a carrier hears, and what the carrier thinks the steward said are very often three different things.
Lastly, working off the clock, which theoretically seems to be a very black and white issue, has shades of gray in reality. While a clear violation of the evaluated compensation system, USPS policy, and labor law, it’s a grievance that local stewards are reluctant to file, due to the appearance of “snitching “ on a carrier and getting them in trouble, which seems to go against the steward’s (and the union’s) reason for existing.