I've been wondering the same thing as my side mirror horizon keeps getting lower. It takes a while to notice the change, but it's been bugging me lately. I have not gotten rid of the tilt as I use that to back into the garage. During this experience I've also noticed that the driver memory does not save the reverse-tilt down mirror position either, which is odd. I've thought about opening a service ticket with Tesla for this, but I've opened enough of those already to fix delivery issues over the past few months.
Another similar issue is that the tire pressure screen positions, do not always match where the tires are actually on the car. I've had this happen several times and am surprised that they haven't fixed this either.