Check in staff at JFK are BA staff. So combined with brusque New York style, and BA standards, I wouldn't be surprised that service ex-JFK is not top notch.
I have had the same gentleman check me in several times for the afternoon HKG flight. I was shocked when he said remembered me from before. He is 'top notch' and gives CX a positive face. However, I have encountered the LAX check-in agents and it is not fun.