Dude use any available drive to store database. Many beginner users install dude packet and set NAND memory as database drive.
My suggest to deny use nand as dude database storage. Allow only external drives (usb/ssd etc) on hardware boards
In general, RouterOS is not about denying configuration made by the admin.
When you install something like dude, you are supposed to read and think a little.
https://wiki.mikrotik.com/wiki/Manual:The_Dude_v6/Installation
That is denying something that is not possible. OF COURSE you cannot select on outgoing interface before the decision is made which outgoing interface to use!
However, that is different from denying something that is technically possible, so this is a wrong example.
(more appropriate would be to come up with denying to set a specified link-local address on an interface for IPv6)