The town of Yarmouth on Cape Cod used to use that trick all the time, raising the assessment but lowering the mil rate.
So one year I'd be in the Assessors office shouting, "Find somebody to give me the $x you say it's worth!" and a couple of years later when they'd arbitrarily lowered the assessment, "You just stole $x from my home equity without a blink!"
I dont think I have to worry about them ever lowering it.