Readers might be later surprised to find that there are vectors which are not lists of numbers

I see this sort of thing as being similar to how physics is taught. Year 1: Atoms are indivisible. Year 2: Well, no, actually, we lied, they consist of elementary particles called electrons, protons, and neutrons. Year 3: Well, technically the protons and neutrons aren't indivisible either. ... Year 10: OK, fine, we have no idea. Your turn, help us figure this out.

Nobody starts rambling about quarks and gluons in grade school, and few practitioners will ever need to deal with them at all. Likewise, for most people looking to get their feet wet in ML, vectors are a 1D list of numbers, matrices are a 2D list of numbers, and tensors are lists of numbers with any number of dimensions. Definitions that are incomplete at best, but good enough to get started.