I negotiated a shorter work day for a few months, years ago, 30 hrs instead of the usual 40. My employer only did it because I said I could do the full days work in a shorter amount of time, which I did, I worked circles around everyone else. (yea, I was probably annoying)
But in the end, management felt they paid me full time, and expected me to Be There, every second of that 40 hrs, being busy, on their schedule, not mine. Period.
I learned to be even busier, do more, train more, filling those hours, because management has a certain expectation; to see your face during certain hours. It's their game, they call the shots.The end. I think that is just the way it is...