That's what the person did -- they put wpa_supplicant.conf to the boot partition -- but somehow the Pi wouldn't connect, and they had no way to debug it to figure out what went wrong.
i had this situation before but i realized i missed a critical step: adding wpa_supplicant.conf BEFORE first boot of the pi0w.
Not saying it's the same issue, but i was scratching my head for a while there.