Honestly, it actually DOES make sense to use separate characters for directory-delineation versus option switches.
There was no way of knowing in 1982 that UNIX was going to take over the world. That everything from corporate mainframes, to desktop PC's, and even phones would rally around the conventions of this largely academic OS.
They wrote papers too (Bell Labs was, after all, a research lab), took sabbaticals, and lectured at universities. I think one of the group (Kernighan?) took a sabbatical at Berkeley that was one of the events that gave rise to BSD?
UNIX was academic, because Bell Labs were forbidden to make profit out of it and thus licensed it via a symbolic price to universities alongside source code tapes.
Had Bell Labs been allowed to sell it, and history would have turned a very different path concerning UNIX clones and its adoption.
There was no way of knowing in 1982 that UNIX was going to take over the world. That everything from corporate mainframes, to desktop PC's, and even phones would rally around the conventions of this largely academic OS.