[cornelis]

Fitness is simply another way of saying an organism has reproduced

It says more. Otherwise all we would need to do is say A is A and be done with it.

How does it say more? The term "fitness" is meant to address the the causes for persistence, not merely the fact.

Fitness also implies compatibility of parts to a whole meaning the organisms persistence is not contrary to its environment. This is also what is meant in the term organism.

Replication requires persistence and that persistence is due to compatibility.

[js1138]

It says more. Otherwise all we would need to do is say A is A and be done with it.

That is all we need to say. Fitness is a restatement of the fact that an individual has reproduced. Nothing else.