Being an occasional visitor to JFK, I can sympathise.
One of the differences between US/UK is that generally in the UK you are given a speed, like 220 downwind, 180 on base and 160 to 4 on final - note these are exact speeds. In the USA it can be a mixture but "XXX or more” or “not less than YYY” is more common as they haven’t the airspace/time/inclination to sort spacing out earlier in the approach, which sometimes causes issues like this as not everyone’s numerical interpretation of “more” is the same.
I wouldn’t want to do 180 at 5 in a 747 but 170 at 5, 180 at 6, 190 at 7, etc. would probably be doable: how to get this across to ATC when you’ve only got 3 seconds of airtime and they’re looking for an argument? “Best speed" I suppose but neither side really knows what that is until it happens.
Got to love JFK, that’s why we use it a lot for command checks (which may have been the guy in question, so go easy...)