Most of those are just handwriting variations of the regular Greek letters though. I know I usually use a lot of those variants in handwriting (apart from varpi) to distinguish them from the Latin letters (e.g. varkappa is preferable to kappa). It seems it would be more interesting to ignore variants like that.

I remember a lecturer who didn’t like saying or drawing xi and so called it squiggle and just scribbled about a bit on the blackboard. I think I also had a time when a lecturer used both phi and varphi for different things in one equation.

I also don’t understand why upsilon gets considered little-used but omicron doesn’t get that treatment. Maybe there isn’t even a \omicron in TeX.

I’m a little surprised that iota is so little-used.

Finally an anecdote from high school: my classmate once became very confused with a derivation on the board involving both k and K because he thought there was also a “middle k” being used as well as big k and little k.