One, that's the problem with raw NAND, like our RootFS is on - It doesn't keep track of bad blocks. That's all up to the OS and filesystem.
UbiFS should automatically mark all blocks bad as they are found, but if you overwrite it with an older version of the FS(like happened with the 0.3x BackupMenu), bad blocks could be marked good.

With the SD card, there is a chip which handles bad blocks; No bad blocks are ever shown to the OS or filesystem provided things are working right, so doing a surface scan won't help anything.
This means that writing a raw image is perfectly fine; it won't hurt anything as no bad blocks are ever read or written.

This is why you are supposed to be testing/using the new version, and -not- the 0.3x series currently uploaded.

FSCK should work(better) in this version, though -IIRC- I don't think there's a "real" check module for UbiFS - it just checks for file coherency.

Restoring should be possible through the restore functionality of the current version, or through making an image and restoring that.