Yes the union was weak, but also the contract had loopholes. For example, it stated that if I had two four hour shifts in the same workcenter that were consecutive, or with a hour between them, I had to make it a 8 hour shift, which had to go to full timers first up to 40 hours each.
So I could just schedule 5 hour shifts and the rule didn't apply, so I could demonstrate that I didn't need 8 hour shifts at all. There was a process to step down the lowest seniority full timers first but over a year you could use the process and get them all stepped down.
Just one example. I don't think it is harder to discipline either here or there. A union does not protect the team the way that most here thinks it will. For sure the benefits are a big deal, but you are tied into a pay scale that doesn't change no matter how good you are, and it creates an us vs. Them environment in the store that IMHO doesn't need to exist in a well managed store.