I've seen a lot of these questions that boil down to "the policy says X" and i spoke to an agent "who said Y", but my situation is actually "Z".

To be honest, I think the best way, if you're in doubt, and have the luxury to do so: Take your carrier (empty) to the airport, and line up for checkin at your airline and ask the actual checkin agent about your carrier and their process. Be friendly, express your nervousness, tell them you got conflicting messages so you want to ask the agent that actually would make that decision. If you're lucky, they would be sympathetic to your concern and tell you how they would really handle your specific case.

Just consider it a dry run.