As I understand it, if you make $1 more than $1M, it's not that you suddenly owe an extra $150k in "back taxes," but rather that going forward, you'll be in the 30% "tax bracket." It's still a tax cliff, and therefore kind of problematic (if it's November 2021 and you've made $950k, you're strongly incentivized to shut down sales until the new year!), but as you say, that's a problem 99% of devs would love to have.