Now that's an interesting idea.
I need to check out the Avesta[0] and track down Platon's Nuptial Number[1] before commenting more, although some obvious replies to your difficulty are that accounting and scribing[2] have traditionally been priesting-adjacent, so there could well be more orally-transmitted relation than we have textual evidence for. (speaking of the latter: my hypothesis up until this point is that even ancient Sumerians had their own geeks who had their own analogies for abstraction, but the reason we now rest the abstract/concrete duality on Platon's broad shoulders is because he was in the first generation[3] who bothered to write their ideas down[4])
[0] although it seems like it took https://en.wikipedia.org/wiki/Zoroastrianism#Manichaeism (after Mani 216–274) to really run with the material/spiritual distinction? (instead of good/evil)
[1] https://en.wikipedia.org/wiki/Plato%27s_number
[2] the spoken word can certainly provide examples of object-attribute lattices that should bootstrap abstract thought, but maybe it was too closely related to our conscious processes for early human fish to notice the water? By the time one is making arbitrary marks for numbers, or even arbitrary clay blobs for numbers with units ( https://en.wikipedia.org/wiki/Bulla_(seal)#Origins ), it should become obvious that both {Bossy,Daisy,Buttercup} and {Cupcake,Ebony,Fiona} can be mapped to "3 cows". Literacy (where one stamps a number for 3 followed by a sign for cow into the clay) makes it even more obvious?
[3] compare Socrates' complaints about literacy, which remind me of our current arguments about LLMs: "but what if someone reads something which has just been hallucinated"?
[4] which might help explain your "and eventually everyone else's"; before writing, it would be difficult for a small fraction of geeks in a population to remain motivated, but after writing it would be possible for them to think "even if I know no one else from my village like me, there have been others, and there probably will be more..." and decide to participate in the literature?