> Why do such comically obvious insider trading if you're only selling a small percentage of your stock?

Because then it makes it look innocuous and fools those who would scrutinize the behavior, like it did may have for anyone expressing the above opinion. It would be so blindingly damning to sell-off all of one's holdings, but selling off a small portion could allow for partial benefit of your asset at peak value before it declines.

If it were me, I'd do it exactly this way. I'd be trying to find the perfect intersection of mitigating the upcoming asset value decline and maximizing perceived innocuousness. Selling everything? That'd be a sucker's move.