Welcome to iRV2! I have not heard of any such law. If there were a law like this it would have affected a great number of full timers.
The only thing that comes to mind is something about the taxable status of home sale proceeds. There might be some difference whether the proceeds went to a another house or were spent on something else like a motor home. But this is a very hazy memory and I am not a tax accountant!
Bruce Dickson 2013 Thor Challenger 37GT, 5 Star Tune, Safe-T-Plus Steering Control with Air Trim, Roadmaster front and rear Sway Bars, SuperSteer rear Track Bar, Crossfires, 2012 Honda CRV on Blue Ox Aventa LX tow bar. Full timers since Jan 2012.