Yeah, that does seem like an important thing to note. But I also think there’s another reason “on wheels” matters. In many areas I think there are actually pieces of land where no “permanent structure” can be built. So that land ends up being exclusively for the use of recreation, like camping, fishing, etc. and that land tends to be pretty cheap because of that restriction. A tiny home would technically be able to circumvent those rules, if properly outfitted.
BTW that guitar amp one is on a foundation, according to the video, so I’m guessing it’s built to code.