I question the "most" here, rather than "all". Examples of J curves that aren't S curves?

>Examples of J curves that aren't S curves?

Reindeer population growth in Alaska.

That's absolutely an S-curve. Any animal population will eventually run out of resources.

Wait a few decades and it will probably plateau at, if not shrink from, a maximum.

Dark Energy astrophysics.

You seem confident an "ultraviolet catastrophe"-like scenario won't play out there, too.

2^x