brumas

I agree with the guy who wrote this article.
If the challenge was to create a piece with hand tools and show his skills in terms of precision of carving, cutting, ... wood, without any precision tool using only hands, his eyes and hand tools to cut, then maybe.

A person like that I might call it a sculptor.
if you look through that perspective, even a square would be cheating.
To do a mitre cut in wood the individual would have to mark it with the pencil the 90 degrees angle just using his eyes and hand and then cut with a hand tool.

I don't think that's what we are looking for, here. We want to work the wood (woodworking) in a precise way and we use the tools that we need and know or even invent, to do the job.

Saying that. I would like to say that, If you challenge your self to just use hand tools, your hand skills will improve, that's for sure,.
But if you go the other way and you are very inventive using the materials and tools that you have in your hands, the sky is the limit, you learn to overcame obstacles and push the boundaries how to do things and shape wood where is not possible in a holistic way.

Well, would be good to add another good book to my library