Earlier quoted context omitted.
Imagine going to a unlimited buffet restaurant per customer and paying an extra $15 and then being told after it is capped at one plate from the salad bar.
Except buffets do do that. Not that extreme, but if you go into a one and continue to eat for multiple hours, you’ll be kicked out despite having “unlimited food”.
Much like the Hetzner article, there's an obvious physical cap that can't be exceeded, and they're supposedly selling up to that cap.