I don't know anything about Boston, but I know that important families in New York were divided in allegiance.
New York City, Brooklyn, and other parts of Long Island had many citizens who supported the British troops. (My husband is annoyed at the way that many New York streets, which were named after early settlers, are still named after them, even though they became Tories).
New Jersey also had many British sympathizers.
Those comments are true but not the same as the earlier ones. It is estimated that about 1/3 of colonists supported the Crown, 1/3 Independence and 1/3 didn't care.
Families were divided (Benjamin Franklin's for example) but that also does not validate the earlier claims.
British support was strong in the Carolinas as well as strong or stronger than in the NE.