Carl,
Maybe United doesn't have this gem in their FOM like we do:
• Differences from written procedures or other instructions should be
brought to the Captain’s attention.
• If, after involving the expanded team as appropriate, the order still
stands, it is to be obeyed.
Hence, at Delta, it wouldn't matter what was in the ACS manual. If a Delta captain says the bag goes in the cabin, it goes in the cabin period.