NYC seems to have its own regulations; I’m not sure how that works in relation to NYS regulations, but FWIW here is a list for NYC: Violation Codes, Fines, Rules & Regulations - NYC.gov/Finance
The only thing I see about a crosswalk is #50, “Stopping, standing or parking in a crosswalk. Note: Crosswalks are not always identified by painted street markings” which results in a $115 fine. So it would seem that there is no regulation regarding being too close to one, just don’t park in one.
As you allude to, I can’t imagine anyone ever getting a ticket in NYC (actually, just about anywhere for that matter) for parking within 20 feet of a crosswalk, and I have never seen or heard of anyone even contemplating adhering to this rule when parking. 20 feet is a lot of feet.