So shouldn't they stop saying it?

That beings are of the same species if and only if they can produce fertile offspring of each sex.

From which it follows that beings are not of the same species if and only if they cannot produce fertile offspring.

But it has been known for some while that Homo Sapiens and several other species of humans have produced fertile offspring.

Actually, no know downside for the offspring, at all.

So, are these different sorts of humans different species, or merely different varieties?

Tracing the tangled tracks of humankind's evolutionary journey

By triangulating the common ancestors of modern day populations, scientists can show that the ancestors of African and non-African people alive today converge at around 60,000 years ago. 

As these ancestors travelled across continents they would have encountered a motley assortment of other archaic human species, including the Neanderthals in Eurasia, the Denisovans in Siberia, possibly a dwarf species known as “the hobbit” (Homo floresiensis) on the Indonesian island of Flores and probably other species that we do not yet know about.

. . . .

[G]enetics shows that the ancestors of everyone outside of Africa interbred with Neanderthals, probably more than once. 

There was also interbreeding with another archaic group called the Denisovans. 

We don’t know much about what these other ancient cousins looked like as their fossils are so fragmented. 

But from a finger bone found in a cave in Siberia, scientists were able to extract high quality DNA belonging to a Denisovan girl who lived about 41,000 years ago.

Intriguingly, Denisovan DNA shows up only in modern day Indigenous Australians and Papua New Guineans, suggesting that their ancestors must have met the Denisovans on their way across the globe, probably somewhere in south-east Asia.