Interesting question. Wonder how a manufacturer would decide a specific model is rated for full time living and how that model differs from the rest of their line...
Advert cost?
It would not pay to say that all were set for full time, so having some that way and others the other, may be a way to broaden the market for the whole lineup?
I'm not an advertising guy but many of the tricks used are common across different fields!
It's not so much what you are selling that counts but what the public believes you are selling!
But then when we look at the question, how we would define a full time RV will vary a bunch, too!
Where it is going to be used and what weather is a big one and who can answer that? When we visited the full time deal for a few years, we never planned to be caught in extremes on either hot or cold, so having single pane glass was okay. But when we went back home for Christmas we would not have wanted to be in the RV!
Two people, intent on trimming down, a smaller lighter, more mobile RV may fit.
But if going full time and a couple kids and home schooled, you may not find one large enough.
We met one couple doing that as volunteers at a park and that looked like a total disaster in the making. My son in law teaches and he commented about what that pair of kids was going to be when they eventually got dumped on the public schools!