yeah, but I know for sure, or atleast the recordable versions of mini-disks are magnetic, even if they are discs.
I have no idea why people are getting confused about the two though
They will not bring out burnable UMD's, because for one thing, they'd have to make a new disc cababple of being burnt to, and I doubt they'd go into that much trouble (which is why they probably made it use DUO memory sticks) so games can't be copied.
The disks anyway are almost unbreakable if you think about it, compared to a normal cd/dvd-rom anyway. When you had megadrive games, etc. You didn't want to burn them for backups did you?