I don't think all Tiny homes can be considered park models. I've seen them being towed on the interstate. Not claiming to know everything about them and can see why some only consider them park models. But the time I spent Googling the subject resulted in both scenarios. One being tiny homes built and permanently parked, and others used by people to tow around and live in for periods of time.
Found
this builder in FL that builds
RVIA Certified Tiny Houses . Couple of interesting links at the bottom of the first link.
So then I Googled
How long you have lived in a tiny home and the results were not surprising.
I'd say that once reality of this lifestyle sets in, it can be a slap in the face.