I agree with you that the Bulk Importer has some inconsistent behavior. However, no Import into the Organizer's catalog should occur until you hit the Import button.
In your case, I suggest that as soon as the dialog opens, you Remove the One Drive from the import list. You can then use the add folder button to navigate to the correct One Drive folder on your computer. (I don't use One Drive, so forgive me if this is not a possibility.)
What bugs me about the Bulk Importer is that whatever you do with it in one session is forgotten the next time you open it.