You are quoting the lab which is all about doing stuff in numpy. Probably if you want to critique the definitions used you should switch to the book.

That said, it doesn't lead with a notion of vector that is as general as I'd like. Readers might be later surprised to find that there are vectors which are not lists of numbers. But I only looked at the first few pages so I assume the vector space axioms show up eventually.

I find it very disrespectful towards a project with such popularity to contributors ratio.

It takes long hours to produce a working notebook, a synergy between concept descriptions and theorical explanations alongside code, comments of code and markdown for the theory here and there is an artistic coupled with engineering stunt you should try to accomplish yourself before criticizing. Perhaps you have, in which case a contribution as the other comment points out is the courteous thing to do.

That book must have taken months to author and is one of the best read on the subject I've ever come across.

Edit: removed incorrect fact about scalars.. they don't have a direction they have polarity.

The book is even worse: "A vector, by contrast, is an ordered collection of numbers."

This is a terrible definition and makes talking about proper linear algebra proper impossible.