i believe that "song for route-finding" was the basis for extra-tribal shared language, and that the symbols made would have been for mapping out the area like an extension of pissing on something to mark it

If it really is structured communication in the form of permanent markings, then it isn't 'long before writing', it is writing.

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Various Australian Aboriginal cultures had message sticks which were inscribed with marks that served as a mnemonic device to the carrier, who would recite their meaning, but didn’t go as far as encoding language independently.

They tended to be so committed to knowledge as a living system, a sort of society-scale memory palace continually rehearsed in songs, stories and rituals, that if anyone had come up with the idea of converting language into writing, it’d probably have been shot down at the suggestion phase as being unnecessary and/or something that could damage the systems they had for maintaining their culture if adopted.