The screensaver is user initiated, e.g. you have to create it, it won’t run of its own volition. So I certainly wouldn’t class it as on-access as nothing is opening this files that you are scanning with the screensaver scan.

The Scan from Windows Explorer also has Exclusions but the Global Exclusion also covers that also, as it too is an on-demand scan.

I don’t know why the duplication is there, perhaps it is more to do with the all of the scans in the Scan Computer being on-demand scans and the AvastUI, Settings Exclusions avoids having to enter exclusions in every one.