Some of these sellers take a liberal approach to the list of vehicles their parts are supposed to fit. Sometimes they just don't know better or they try to attract a broader customer base and hope the buyer knows what they are looking for.
Especially ebay is terrible for the "fits" category, which will list everything you want from a Honda Step-Through to a Bugatti Veyron.
You are well advised to ask a lot of question BEFORE you buy. If the seller does not respond, don't buy.
I don't know for sure, but I would assume, at least the late 250SL has the "Pralltopf" steering wheel, which will make it a tad more difficult to adapt a classic aftermarket wheel not specifically designed for it.