I booked direct with Emirates over the phone — all one reservation. I like you am amazed that both airlines are not able to say for sure. I have phoned numerous times and seem to get a different answer every time to a question that should be within the airlines’ area of knowledge. That is why forums like this I am discovering is a better source of information. Normally, I would just take my chances but the main issue is the visa one. The Vietnamese Embassy has already told me that if I leave the transit area I will need a visa to reenter. There is no visa on arrival in Vietnam. I travel in October, so I will post when home.