Those who believe that the Neanderthals were a different species call them Homo neanderthalensis
(no sapiens
in the name). Yep.
Q: If you call a tail a leg how many legs does a dog have?
A: Four.
Calling it a leg does not make it a leg....
Scientists do their best to assign accurate genus and species names to extinct beings, but 100% certainty isn't always possible. There are several types of hominids who are classified as part of the genus
Homo (and therefore could be considered "human" since that adjective comes from the Latin word
homo) and there is disagreement about how many species are represented among the fossils found to date. And there could be future discoveries that will force changes in the family tree.
If evolution occurred in the way biologists think, then one species developed out of another--so the boundaries between species are sometimes fuzzy. Dogs are regarded as a separate species but they can interbreed with wolves.