When I took a comparative languages class in school, the teacher said that
the complexity of a programming language varies with the square of its
number of features.

I wonder if it's similar for command line options in shell-callables?

On the other hand, adding command line options was (at least at one time)
seen as a way of distinguishing GNU tools from Unix tools - that is, they
were seen as a way of avoiding the copyright lawsuits that were snipping at
BSD's heels.