AFAIK /dev/sd* discovery and ordering was never guaranteed to be
deterministic nor persistent across boots nor match any hardware or
firmware ordering. One should not rely on these names, hence the use of
persistent identifiers such as UUID, device path or disk ID.
I agree. That is why I used UUID for the fstab entries. But this drive
ordering issue is specific to the installer. The preseed is expecting
a /dev/sd* type of entry in order for partman to partition the correct
drive...or in my case (using software RAID1) drives.