Are you sure this is true? I learned to scuba dive just over a year ago now and the ok sign was taught and was still in the course theory books.
It's true. For the time being,
some of them acknowledge that it's not
always a white supremacist symbol (in reality, it rarely if ever is) but that will probably change and of course they will claim it's a white supremacy symbol whenever they think they have something to gain by doing so.The origin of the story is known - it was some jokers on 4chan trolling the professionally offended by making the knowingly false claim that the "OK" symbol was a white supremacy symbol, to see if any of them were gullible enough to believe something so obviously nonsensical. It turned out that many of them were.
Oh and nitty gritty to me means digging into the detail of something. So perhaps digging, dirt, yeah could have come from slavery I guess, not that it matters.
The fake etymology is that it refers to general detritus at the bottom of slave ships. Which makes no sense, has no connection to the meaning of the phrase and would require time travel since the phrase didn't exist until the mid 20th century. So no, it can't have come from slavery. But you're right that it wouldn't matter if it did, since the phrase itself still wouldn't have anything to do with slavery even if the fake etymology was true. Which it isn't.