A) It's anthropology. There is nothing concrete available; the entire field is an attempt to learn things by investigating human societies. In this case, the allegation is that a specific tribe have enough stories about human-like but non-human creatures in their region to be taken seriously (in conjunction with the established presence of non-human hominins in that region in the fossil record) as a record of recent history.

B) The article is promotion for a book, which I would hope would have a more cohesive presentation of evidence.

If the book had anything compelling it would already be news.

It’s an interesting and fun subject, but I expect the book is as full of facts as this article.

It’s easy to find “facts”, when I was 12 or so I got a book about the Bermuda Triangle and was thoroughly convinced that Atlantis was real and had advanced technology in ancient times.

Does it need to? It's hard to expect "concrete" reasons for "might"s and "may"s. Even without them, the information is still interesting.

The author points to 30 eyewitnesses he has spoken with and that the current evidence doesn't rule out his proposition.

Only of you consider advertising a subspecies of navelgazing. Available in May 2022.