Hi Kevin
I tried out, as you described with a fresh install. I added?dtoverlay=disable-wifi as last line to config and rebooted. After reboot I typed ip a and wlan0 was still present. So I shut down the raspi and started new. Now pi a showed no wlan interface. I connected the dongle. ip a now showed again wlan0, I rebooted again, the raspi connected to my network, I typed again ip a and the list showed wlan0 and wlan1 again. So actually I do not know, which adapter is used
klaus, DC2JR?
dc2jr