My Grandpa always said that 'nothing' was always or never and I've found that to be the case in 'most' cases. It probably applies here also. However, my only encounter with Unions has been on two occasions, once in the Musicians Union which was out of necessity but for a very short time and the other was when I was hanging drywall in the Rocky Mtns of Colorado. The latter caused me to think about some of the Union's thinking at that time.
Case in point: My partner and I were hanging drywall by the square foot in Condos in Summit County Colorado (non-Union) and then one day, because of the lack of work in Denver, I suppose, some Union hangers came in and started working by the hour (whatever scale was at that time). Anyhow, we would hang at least twice the amount of sheetrock that they would and therefore we made more money (that was our entire purpose - - "to hang as much drywall as possible" ==== $$$$$$$) Now we had no problems with the Union dudes because they were far less competition than other hangers that hung by the square foot as we did. However, one day the Union dudes came over to the unit we were working in and told us that "we were taking food out of their families mouths by hanging more and making more than they were ! ?????????????
We very "politely" told them that we preferred get paid for the amount of work we did rather than the amount of "time" we were on the job site !