The statement was:
Personally, I would go to the root of this and don't bother with on-demand scans.
This implies that the functionality of the on-demand scanner is fully superseded by the all singing, all dancing resident scanner. And it isn’t.
This isn’t about my choices on my machine. This is about providing accurate information to everybody reading this forum. Being aware of the exceptions as they exist.
An unmounted ISO will not be completely scanned at download (nor should it), and an infected installer will most likely only be stopped mid-unpack/mid-install and leave a big mess to clean up.
I agree that hopefully mounting the ISO will trigger the resident scanner, but then it would still only scan with its default settings which are as I understand less scrutinizing than an manual on-demand scan of the files/folders inside. And in the case of an installer you really would prefer to force a scan of the whole thing before starting the installation. So again: using the on-demand scanner. So it either clears and the installation will complete, or it gets blocked and no cleanup is required because no install was initiated.