I read a bit more. There definitely was introgression of West Eurasian populations into East Africa and Sudan than percolated into West Africans to the tune of about 15 million base-pairs of sequence tagged as Neanderthal. Not sure we have values for how much Yoruban ancestry is now embedded in Mbuti genomes, but it is small. So the flow of Neanderthal genomes into Central African hunter-gathers will sub-decimal dust.

But having said all that, maybe the key point Zimmer is making IS a good generalization.

I think it is a fair generalization at this point. Mbuti also have a ~6% West Eurasian admixture signal using an ancient (4.5kya) Ethiopian individual as reference, though Pickrell 2014 did not see it. Decimal dust, perhaps? https://www.science.org/doi/10.1126/science.aad2879

The ghost admixture story(s) will turn out to be much more localized, I imagine.