If a provider books a Hotel in Manhattan, is it a best practice to list in your ad that your Anon Hotel, (mention no name of actual hotel, obviously, or even it's rough geographical location) is a non-keycard, button operated elevator?  I assume a local guest would already know about parking options, and anyone visiting the city is already versed as well, so mention of parking ease would not be needed also.

I only experienced a keycard elevator once and in that situation the provider had to come down while I wait near by and she got me. In that case it wasn't known in advanced, I had found out when I got to the hotel and the assistant told me to wait near by the elevator. In all my other experiences, it's never been mentioned though in the ads and its never been an issue getting on. I think it's worth mentioning to the person that books with you to give them a heads up once everything has been schedule. I can't imagine someone would decline seeing a provider because an elevator is keycard only.

No sense making Uncle LEO's job easier. The number of hotels without keycard security is rapidly dwindling.

Rapidly dwindling - really?
I always use 4-5star hotels, and have only booked two ever in NYC to find out that they required key cards

I assumed the 4 or 5 star rule of thumb is best in booking in Manhattan at any rate.  Thanks for confirming my logic.