Fwiu, once upon a time, every local had a big book of supplemental grievance decisions. This has given way to horse trading and backroom deals, based on "who gains what". A lot of the locals only want to keep the peace, in hopes of gaining more work. The old "past practice/maintenance of standards" absolutely no longer applies.
I was sold out by a BA in PA over solid layoff language, at the beginning of COVID, because the BA and the guy that ran my company vacationed together. I guess when I said "my guys could die over your cheap load"the BA heard that and worried about losing his spot in Myrtle Beach. We all quit shortly thereafter.
Fwiw, this was a white paper contract based off the old nmfa steel supplement.
The ibt is "only" 3/4 as scummy as your local management, in my experience.