Because they’d eventually have to disclose when the vulnerability was discovered and that’d be extremely obvious what they’re doing?

It might be obvious, but that's exactly what Brian Krzanich did in 2017. He didn't get in any actual trouble for it even though the timing smelled blatantly like insider trading.

Is it obvious if they have an existing plan to sell shares and are simply waiting for it to trigger? They can reasonably claim they took this action to protect consumers until they had a better fix

Executives are allowed to sell at pre-agreed dates. If they do it on those dates then there’s nothing to prove, they just postpone the disclosure under any reason. Doesn’t make it smell less like insider trading, you just can’t prove it.

I don’t think he did. He got out and had a prior years notice. Then he made a comment about not losing over 20 percent datacenter to amd. Dude definitely seen what was coming

Seemed to work out okay for the Equifax executives who sold stock before they publicly disclosed they had been breached.