Its is actually possible to have a reroute reduce pay and I had it happen more than once. It has always been quite common to get rerouted going through major hubs. 25 years ago we used to bet each other if we would get a reroute going through ATL. The way you lose money is if early in the rotation you have made a bunch of time increasing the value of the rotation and then you get rerouted. You are only guaranteed the original value. I don’t recall anyone really *****ing about reroutes back then because most of us considered it part of working for a airline. We didn’t get all the extra pay awarded now either as the contract simply paid you your original trip or the value of the reroute whichever was higher at straight rates. I was once rerouted from a turn into what ended up being 7 days. No premium pay. The SO did try and expense purchasing additional underwear but was denied!