Many mainstream Christian religions disagree, citing various conflicts with Christian doctrine. https://en.wikipedia.org/wiki/Mormonism_and_Christianity#Chr...
In any case we could get bogged down in definitions and semantics, but if you come down on the side that Mormons are Christian, they are still probably the most interesting subset to break out into their own subcategory.
Or if they are then I think Muslims might also qualify as they also believe in Judaism + Christ + one more prophet. Though depending on who you ask they might require Jesus to be part of the holy trinity and not just another prophet.
PS: Granted, I think the general stance with most people is simply let religions self identify as plenty of religious debates end up with one side killing the other.
Since JW is usually categorized as Christian, I think valine's test should be considered approximate rather than exact.