I have never considered the synology list for disks and have never had a problem. The latest ones were even disks that came out of a NetApp server with modified firmware and everything worked without a hitch. I would say that the synology list is simply there so that they can cover themselves in case of a problem.

Normally the reference marked on the disks should be on the Synology compatibility list.
In a My Cloud, it can be special disks (not usable) or WD Red (usable).
Otherwise with empty disks, yes it is easy to install DSM according to the usual procedure