100 times as many humans, randomly mix in the lesser number of Neanderthals for breeding and they would be 'absorbed'.
Except you can't randomly mix them in.
Why would I allow a Neanderthal man come to my tribe and mate with my tribes women? Why would I not just kill him?
I get I'd also be at war with other tribes killing their men, but Neanderthals I assume are easy to kill tactically and emotionally and I wouldn't expect them to be good allies.
You can't just make these theories without explaining the mechanisms.