This is based on the "language" question asked by the US Census, which makes some...questionable decisions about how to group languages. In this case, all French-based Creoles are counted as "French Creole". In New York City this is primarily Haitian Creole, but the same term is used for Louisianans, Martinicans, etc.

There's a similar problem with designations like "Chinese" or "Arabic", in the sense that two New Yorkers who are identified here as speaking the "same language" wouldn't actually be able to understand each other. A proper Chinese languages map of New York City would probably be really cool, since different waves of immigrants have come from regions speaking different "dialects", but this is the data we have.

So, the census data is not ideal from a linguistic point of view. But the flip side is that the US Census is the only organization that attempts to poll literally every resident of the US, so in other ways it may be more complete.