"Birds of a feather, flock together." so the expression goes. Put yourself in the shoes of someone who owns a park model. Park models are designed and equipped to resemble a half-way house and trailer. Basically, I think they are just shorter versions of mobil homes, and more mobil as people do not remove the wheels or tongues on park models like they do with mobil homes.
Nothing wrong with a "resort" or a "park" that has occupancy with park models. You're correct however, that park models can (and probably are) used for a permanent residence, but how many "traditional" full timers do the same thing with a more standard "mobil" RV?
If the Park Models have found a happy destination spot, I think that's great! It doesn't affect my world in the least. If I am fortunate enough to get a "spot" to park and right between to Park Models, I'm still thrilled, simply because I did get a spot! I'll be moving soon enough, much sooner they they are. They're honkered down for the "duration". My "duration" is much shorter. But hey, those folks are just as friendly, just as courteous, and just plain ol' people like me.
I see no difference there than a campground that has 1 or 2 campground "hosts" parked for several months at a time. The only difference is the type of RV they have. Other than that, I see no problem.
But, if you're talking about "seasonal campsite" vs non-seasonal... well ... that's a different matter!