Yeah, that property is what would create the sigmoid curve in the ideal case: PoW chains aren’t inflationary (rather the opposite) so competition reduces mining margins to effectively zero, which translates to fewer and fewer people bothering to grab at surplus profit as the number of miners grows and that surplus profit goes to zero.

It’s why you see consolidation into mining consortiums. An inflationary PoW chain wouldn’t have that — everyone would be incentivized to mine for themselves (like a gold rush.)