I've been a S&W pistol fan for a long time, but admit I've never seen or heard of a steel framed 469 or 669. SCSW indicates there was a short distributor run of satin nickle 469s, and the 669 had a stainless slide and natural aluminum colored frame, but both were aluminum alloy framed pistols. The only steel framed compact 9MM double stack guns I can recall off the top of my head, are that run of PC Stocking Dealer guns that came in 9MM (SD-9), .356TSW and .40, IIRC. They actually did have stainless steel frames. I never say never though, so perhaps a more knowledgeable member of the forum will come along to shed more light on this.
It is possible some company produced an after market steel frame for the 469 and the original frame was swapped. I've never seen such an after market frame for the 469 and can't imagine there would have been much call for such. The 469 did not have that long of a production run and it was made to be a lightweight carry gun. It would not have been profitable nor much demand for some company tooling up to produce a steel frame conversion.
Most likely in these type reports are either 1) the person claiming doesn't know the difference or 2) they know the difference but trying to scam an uninformed buyer.