Humans began to rapidly accumulate technological knowledge 600k years ago

News article says humans, but earliest human (homo sapiens) was around 300kya. The actual paper uses the word hominids rather than humans.

The word human is commonly used for both modern humans and members of the entire genus Homo. Hominids is a more general superset that isn't strictly correct here. The term hominin is more appropriate in this context and what they actually use in the abstract.

In my opinion though, "human" is the better word here for conveying the right mix of informality without implying the specific semantics of "Hominini sans Pan".

Is it?

This is literally the first time Ive seen the word human applied to other hominids. I see many discussions about neanderthals and denisovians and so on. I have never seen them referred to as human.

I'll admit this is the first I've encountered the concept that "neanderthals and denisovians and so on" are not human. Maybe not biologically modern humans, but I'd certainly consider them fundamentally human.