That formulation has the same problem. Like “always swims left”, “only swims left” suggests that every observed movement is leftwards.
Unless there is an implicit distinction between purposeful movement, analogous to swiming, and some drift due to chance.
I doubt most people who read the phrase “Cthulhu only swims left” would pick up on that unspoken distinction, though I could be wrong.
That formulation has the same problem. Like “always swims left”, “only swims left” suggests that every observed movement is leftwards.
Unless there is an implicit distinction between purposeful movement, analogous to swiming, and some drift due to chance.
I doubt most people who read the phrase “Cthulhu only swims left” would pick up on that unspoken distinction, though I could be wrong.