I see what you are saying, but to make a blanket statement DO NOT PAINT THE FRAME is misleading. Painting the frame with a good paint won't cause any harm. But, spraying it with a thick "undercoating" like Ziebart is a very very bad idea.
My preference would be to do BOTH: get the frame very clean with a strong degreaser (Purple Power, Super Clean, etc) and a pressure washer, then go to town with brush-on Rustoleum Satin Black. Give it a few weeks to dry/cure, THEN give it a good coating of the oil-based rust preventer of your choice, be it Wool Wax, Fluid Film, or whatever. Repeat every year.
I have mine sprayed every fall by a local shop that uses the NHOU product. It's really good stuff, odorless, doesn't seem to wash off, and best of all I don't get the nasty unpleasant job. I drop the spare tire and all the skids and deliver it to them. $200 to do the whole thing.
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