First at 11 years we really should replace them (yes I said WE but I got another higher priority repair, Tires are #2)
Second. "Flat spotting" on a tire is something else entirely Now if you move the RV in very cold weather the tires may be "Flat Spotted" from sitting for, oh, the first 2 or 3 revolutions, but not much farther... I don't think taking weight off with the jacks will affect that.
IT does, however have several other advantages
Stability.. Jacks, or in my case hard jack stands are way more stable than sitting on springs... I was just far closer to disaster (Hurricane) than I care to be.. Rig did not shake very bad.. Due to a jack failure it's sitting on jack stands. Nice solid jack stands.
It also takes a load off the springs.
