Thanks, although I don't know why I even added that part as it's not relevant to my example.
In any case, you are correct. If you are using folders, you could have folders on one, some, or all of the drives. It would depend on how it's configured to use free space and when/if data was added to the folder. If the folder was present on a single drive when that drive was added to the pool and nothing new was added, then that folder will only be present on that drive.