Notice that it's the NYC Police Commissioner calling it terrorism...a local .gov agency.
The feds are unwilling to acknowledge Islamic terrorism. See no terrorism, hear no terrorism, speak no terrorism. Islamic terrorists in the US and elsewhere Do Not Exist.
Local and state governments and government agencies may or may not have the same point of view...especially when an Islamic whackjob attacks four of their employees and citizens and the local citizens have a lot more influence come election time.