The context of the article is a tech employee getting ESPPs. Such a person is already nearing the top of the tax bracket anyway. It's at most going to mean two or three percent difference on just the capital gains. This is, for almost everyone, going to be a completely unnoticeable difference in practice.

Let's say you make $100,000 and a whopping $50,000 of it is RSUs and ESPPs. You've been very lucky and the stock portion is now worth $75,000. You sell. Your federal bracket has gone up by 2% and your California bracket has stayed the same. You will owe an additional $500 in taxes. This is just about the worst case scenario where you're not making that much for tech and your comp is exactly on the edge of a tax bracket and your comp is 50% equity and your company went up by 50% since vesting.