"Auto Update apps" is for CIQ apps, and not the firmware.
On the vivos, FW update always gets pushed to the device, as for support reasons they want you on the latest FW. If they didn't do that, and you were reporting a bug, the first thing they'd have you do is update the FW.
Yes, I strongly agree Garmin should find a solution to choose firmware update or not by user. Especially when the users are doing their race or practice and every second counts.