This rule worked for us in September 2014 (coming from Finland). It also helped that the guy from our accommodation was waiting for us, at the visa-on-arrival desk, working things out with the visa lady.

The guy next on the line got stuck as he was in Maputo for business and didn't have proper paperwork with him. I don't know what happened to him eventually, he started calling the place he was coming to visit that he can't get through the visa on arrival desk.