I would NEVER go by what an airline employee or government official has told a passenger verbally. How is a passenger supposed to explain this to the airline at check in? The only way to verify such information is for the airline to contact the relevant government authorities, which maybe sucessful or not. Obviously, the first thing the airline employee will do is refer to the data on their computer systems and follow those procedures.

If visa/immigration/exit requirements are complicated make sure to travel with a printed copy of what is needed to avoid being denied boarding. As bad as the op's cousin in law's situation is this entire thread should be a reminder to all on FT that is it necessary for the passenger to ensure their documents are in order and refer to the necessary government publications on entrance, exit, visa requirements and other terms and conditions associated with their travel plans.