For simplicity sake, a 10% tax on income would scale infinitely, no matter how big an economy grows (I’m not arguing in favor of this tax).
But the point of the article, in my opinion, is that US has a large problem, costing tax payers an estimated 40 billion in labor figuring out their taxes, where other countries have almost automated the entire process.
I think there is something to be learned from there, as most people would agree that the US tax system is a mess.