When making an item for yourself, like the kayak paddle in the article, it makes good sense to use your own body measurements as a starting point.
I have heard of a modern harpsichord maker, who starts every instrument by defining the inch for that instrument. If I remember right, it was the width of the wide ("white") key. Everything else was derived from that with geometric methods, so the proportions of the instrument came out right.
I have read that in the middle ages, most European cities had engraved some (local) standard measurements in the walls of the city hall. That was good enough when there was not big need to standardize things. But today things are more international. A German M6 nut is going to fit on a Chinese M6 bolt, without any big discussion about the thread pitch etc.