Sadly I didn't have the time to read it all, but I note that your authors also talk of a cultural-based "shift in speed of artifact change 300‐200 ka" and maybe (or maybe not) also another (?) cognition-upgrade based shift 100-45 ka, which would be that "creativity explosion" that you are talking about ?
They also talk about individual learning as a third mode, which somewhat ironically seems to be what the autism article is talking about... except the conditions for it are genetically based ! (But I guess so is the transition to mostly social learning?)
EDIT : Hmm, and since autism is "anti-social" (and also probably generally anti-survival and anti-reproduction), may it be that it was only once that large, stable, strong social groups were put in place starting with 300-200 kya, that the conditions for "autistic specializations" could emerge starting with 100-45 kya, and this is what in turn turbocharged inventions leading to the "creativity explosion" ? The autism article would make a lot of sense under this light !
Anyway, perhaps we can't cleanly separate nature and nurture, see also recent discoveries somewhat rehabilitating Lamarckian inheritance.
Also, my author in a parallel article says :
https://loukeep.substack.com/p/vagaries
> The first modern human bones are in Jebel Irhoud, Morocco, 300 kya. H. rhodiensis - the African variant of heidelbergensis - disappears at around this same time. There are just-about-simultaneously collections found in the Rift Valley, Kenya, that point to incredibly “modern” behavior[1], including pigment production and obsidian distant enough to suggest trade networks. Once, I think, it could be maintained that some kind of “great leap forward” in human behavior took place some 60,000 years ago or so. I don’t particularly understand how one can keep that up now.
[1] https://science.sciencemag.org/content/360/6384/90