Of course it’s a matter of documentation, and users not reading it.
The user interface offers three choices. It says it will take some time to do the full factory restore (which, BTW, is likely to be secure enough so that nobody but the likes of NSA will be able to recover data from it). It gives you the choice of dropping back to the quick method.
If you’re disposing of your mycloud, or returning it for RMA, if you’re sensible, you’ll do an overwrite erase, which is what the Full Factory restore is for. That erasure, on ANY 4TB disk, is going to take some time. I’m happy to wait for that length of time if I want to permanently destroy the data on the disk. If all I want to do is clear it down so I can use it again, I’ll do a quick factory restore, which just wipes the settings and disk indexing.
If you CBA to read the documentation, which is quite well indexed, then don’t complain if you make mistakes when driving the thing.
Would you found it reasonable to get on a bus to your next town but the bus with route through 10 other countries before reaching your destination?
Would you get on the first bus you saw without looking at the route map and timetable…?