but maintenance can prevent it.

You absolutely can, maintenance includes a carwash every now and then. A couple times a year with a garden hose cleaning out the frame will prevent what you have. My 05 frame looked nothing like yours, I maintained it.

Ridiculous thing to say. Washing, coating the inside with fluid film, putting a fresh coat of paint on the frame every year or two. That’ll have you completely avoiding any major frame rust.