These inscriptions date back to hundreds years before the formation of Andronovo culture.The proto-Iranians emerged in the Andronovo culture which covered a vast area from central Siberia down to central Asia. What you claim only proves that these early Iranians expanded into what is present-day Iran very early on, not that they originated in Iran. The Scythians and Cimmerians were much more representative of those early Iranian peoples and they were from the steppe.