I don't remember how those "blessings" work in this kind of situation... are they stored on the filesystem or in nvram? If in the filesystem, it shouldn't be an issue, but if in nvram or such, maybe it still would work if the partition setup is similar? Unless it stores more info about hd somewhere... but at least for MorphOS part it's easily fixable with HFSSetMacBoot if it becomes an issue.