Reordering cards before and after sync and tagging cards after sync makes more sense to me than doing both at app start. For example, a typical workflow when adding cards to Anki on PC:
Add X new cards.
Need to sync these to AnkiDroid/etc, so cards must be reordered.
Sync happens.
Cards may have been added by other devices. Therefore, they must be reordered. Incoming cards might also need to also add tags.
Reordering cards before and after sync and tagging cards after sync makes more sense to me than doing both at app start. For example, a typical workflow when adding cards to Anki on PC: