Unix doesn't use double dashes for options; that's a GNU thing, and, as everyone knows, GNU's Not Unix.

Normally the Unix/GNU opposition is irrelevant at this point, but you managed to pick one of the few significant points of difference.

If that's what you use as your yardstick of what's Unixy, then I guess you don't consider "find" to be Unixy, in spite of being one of the early Programmer's Workbench tools.

Short options were a compromise to deal with the limits of the input hardware at the time. Double dashes were a workaround for the post-dash option car crash traditional Unix tooling allows because teletypes were so slow. There is nothing particularly Unixy about any of these options other than the leading hyphen convention.

OCaml using single hyphens is not un-Unixy.