I recently read an article by my good friend Randolph about not using a windows mounted ISO to install SQL server. This got my thinking, I have seen issues before. I’d say 98% of the time it works fine so the problem is rare but I have come across it before. Therefore I also don’t recommended installing directly from the mounted ISO. A hypervisor mounted ISO works fine or copying the contents to the drive also works.
I think this is also a good time to make the point not all systems are the same. Just because I have no problem running a SQL install over a mounted ISO over the network for one client doesn’t mean the same situation will work for another client. Often we get spoiled with fast hardware but that isn’t always the case everywhere you go.