Many RVs are opportunistically, euphemistically, or optimistically marketed as 4-season rigs.

(Which is a claim somewhere between wishful thinking and outright balderdash.)

If I go buy a Marmot 4-season mountaineering tent, now THAT’s a 4-season living space. A mountaineering tent is a double-wall engineering miracle made of 70D ripstop nylon. It costs as much as my car. It’s a portable shelter designed to withstand Arctic blizzards that could literally peel the skin off your face. -30 degrees and snowing? No problem!