I'm not sure time-to-change is all that relevant; it didn't take 100 years for the eggplant emoji to come to mean "penis"

It also didn't come to mean that at the behest of those in control of the glyphs. It came to mean that in an organic, even memetic fashion. That's the difference.

Slang can change rapidly based on current events.

It doesn't change very often due to top-down orders, though...

It didn't in this case either, it changed because a group of private platform vendors decided they agreed with the rationale one of the other vendors had for changing something.

Why do you not consider that to be "top down orders"? Sure, the orders came from a few execs at a few companies, rather than from the president, but it still looks top-down to me. Specifically it looks top-down in contrast to slang changing rapidly due to current events (which was the original context), which involves a bunch of people having a new reference point, and choosing to use that in their speech.

So not very far away from an oligarchy as paulddraper pointed out?