I think the point the parent is getting at is that nothing about business guarantees constant, compounding growth. It's not just mathematics, it's population growth, productivity, capital distribution, etc. - lots of stuff that we take for granted that results in constant growth rates, but that doesn't necessarily have to.
Compounding interest could continue at the upper right part of the S-surve. If the interest decreases every year, and sufficiently fast, it could give rise to a convergent infinite product. So total wealth would never exceed the threshold of the possible.
While physical laws do not bound mathematics, they bound the reality and context in which we talk about "compounding interest."