No it wouldn’t. Not to a similar degree of scrutiny. Certainly not with default settings. It takes some time to plow through all the files of a large iso with a on-demand scan, so activity like that from the resident scanner would be very noticable during download. It doesn’t happen.
The default setting of on-demand scans, wouldn't be scanning ISO files anyway, so you would have to have enabled that in the scan settings for Packers.
I’m not manually scanning the ISO itself. That is no different than the simple quick resident scan during/after download. I mount it and then scan the actual contents. As a folder/drive. Exactly because otherwise it will just do a superficial scan. Scanning the contents takes way longer this way because it is a deeper scan. And I actually prefer this over enabling more exhaustive default scanning in the resident scanner, to include packers for instance. It does mean there is a role for on-demand scanning, and this is a good example of that.
Another example is that by default, archives are not scanned thoroughly. Which is good from a performance perspective. On extraction the resident scanner will do a more in depth scan, especially on the executables. Anything sketchy will be blocked. Now imagine this during an install near the end of the process. Half the program/game/whatever is installed, and then the installation is halted before the uninstaller is installed. This has happened to me in the past. It is a pain in the rear to fix. A on-demand scan beforehand prevents such messes.
