A four day work week is only another pay increase if you're talking about a salaried worker. The kind of worker represented by UAW is not generally overtime-except, so they don't get paid for hours they don't work.
I somehow don't see UAW arguing for a reduction in pay. The four day work week is more often than not accompanied by a related pay increase so the total pay per week remains the same as a five day work week. The benefits are supposedly a better rested and production workforce, which has yet to be demonstrated in the type of setting UAW oversees.
You're inventing terms that are not discussed in any source I can find. The sources I see show a 4-day work week and a 40% pay increase. If you can find evidence of a second pay increase we can talk, otherwise I'll assume that the 40% is meant to be that increase.
You led out your initial comment warning about propaganda—it might be worth considering if you fell for propaganda on the other side.
