I have quickly scanned the Phd thesis [0] and regarding the citied (basically the same sources as mine above) DNA analysis and fossils found (carbon dating) the uncertainties in the measurements themselves are given as evidence of "denial". Apart from presupposing a "western mindset/bias" there is no clear pointing evidence given to the contrary other than the indigenous oral/cultural history; it is after all a Phd in "Indigenous Studies". So, the biological hard evidence (phylogeny/populations) seems pretty weak.

But of course one should be open to the possibility, there are a lot of twists, turns, dead ends ... in history (we have very limited datapoints), especially farther afield.

[0]https://m.box.com/shared_item/https%3A%2F%2Fapp.box.com%2Fs%...

The overlap between the last known modern horse and the first people in America is about 2000 years. If they domesticated horses in that time, how come the horses didn't thrive along with the human population?

I think the horse population where already on the brink of vanishing due to climate change after the last ice age, and the new Americans simply ate the last of them.