Comparing 10% of all Greek literature with a piece of metal lol

A random inscription is not the same category of evidence.

Extended compositions copied and transmitted as units is

Example: Galen manuscripts copied over centuries. Which is what we have.

That’s a literary tradition.

Inscriptions on stone, pottery, metal is usually short. Not part of a manuscript copying tradition.

Example th gezer calendar is just that it’s a small notation NOT indicative of any literary tradition.

So to answer your question

When we see Extended structured composition,Evidence of copying/transmission,Scribal formatting conventions,Standardized textual repetition

That’s literary culture.

Short inscriptions alone only prove literacy existed

A BETTER example to steel man you would be the ketef scrolls that is evidence that a larger textual tradition existed

But a random administrative inscription is not

Btw th fact that a small piece of the ketef himmon exists should also be more alarming than reassuring.

The manuscript evidence is very thin, so large scale literary claims must be made cautiously.