Was UAW for 43 yrs. As far as profit sharing it sounds great. We had it at various times at the parts supplier I worked for. Trouble was books and figures are cooked so they don't show the set goal. How do I know this? My then foreman was POd that his dept. didn't show the gain he knew it had done. Why? Because in midstream they changed the way it was figured, result, no bonus.
As far as why the UAW picked GM they have always targeted one of the big three knowing that the other two will following lead of the first