Before jumping to more speculations, and start throwing stones ( Korean pilot flying in China, bad english of ATC, etc, I smell this coming )may I remind some of you that ATC is normally done is sectors with different frequencies/different controllers. What was declared on one frequncy was most probably not head by the controller handling final APP and/or by the A320 crew. How this was relayed upon, which words/language were used to convey the urgency, could perhaps shade some light to this incident. If you're on very short final , were cleared to land and going around means tons of paperwork in your non-just culture airline you might decide differently than most of us would.
Back to Avianca/NY : since then fuel emergency is declared ealier, but still language used is often misleading. Crew tend to mention tons or pounds of fuel, while controllers are interested in minutes remaining. "2 Tons" means little to ATC.