I'm not quite sure what you're talking about.
However, Urban Sprawl is a problem around a lot of cities. Oregon has tried to have land use planning. But, perhaps it is failing.
20+ acres are often working farms. Perhaps even 10 acres. But, 2 to 5 acres, and they're just home sites that people mow super large lawns.
A few years ago there was a ballot measure that essentially invalidated minimum parcel sizes.
Ballotpedia: The Encyclopedia of American Politics
ballotpedia.org
So, if your family owned property before it was rezoned to say 20 acre agricultural, or some large plot forestry zoning, then it would require the government to say make up the difference between perhaps 1 acre zoning, 5 acre zoning, 20 acre zoning, or 50 acre zoning. Essentially invalidating the whole zoning. At least for certain older property.
Many of the old farm houses from before the 1950's just need to get bulldozed and replaced. Tiny, falling apart, and nothing worth much in them. The lot is more valuable than the house.
I haven't paid a lot of attention to manufactured homes for quite some time. There is a manufacturer near Albany, Oregon, that used to advertise a lot. I have a second cousin in Nevada that got a 2 story (or one story + basement) manufactured home about 30 years ago. It seemed like a neat concept. But I didn't realize they had made it to Oregon. I haven't stayed in touch with that family, and unfortunately the whole family didn't survive well.
Manufactured homes are unique. They can have good insulation, but they seem to cut corners absolutely everywhere in the manufacturing.
I have an acquaintance that has 5 acres. It came with one partial house (not a fully functional legal house), and one single wide trailer that had an attached enclosed patio/living area. They moved in a double wide. And another single wide.
Now planning to tear out the original single wide and moving in a new double wide.
And probably build a stick built tiny home.
That tiny lot currently has 6 adults living there (2 disabled), and 2 more coming. I'm not quite sure why the government hasn't just said NO.