Have an expensive Basic Economy ticket to Cabo San Lucas that I need to cancel due to a positive COVID test. I reached out to two different chat agents as well as a phone agent, and unfortunately have been getting different stories depending on the agent. Hoping someone is able to answer the following:

• It sounds like as an exception to normal Basic Economy rules, they'll issue a Flight Credit (cancel the ticket and leave the value 'open'). This seems consistent between agents.
• Validity period - some agents say it's 3 months, some 6 months, yet in general a Flight Credit is valid for 1 yr. Is there actually a special Flight Credit that you have to use within 3 or 6 months if you cancel due to a positive test?
• Destination Flexibility - one chat agent says the new trip can be to a different destination, one chat agent says it must be the same destination, phone agent says it depends which person you get when you call to do the rebooking. Normally a Flight Credit proper can be used for a different destination...again I guess the question is if there is some sort of more locked down version of a Flight Credit for these situations?
• Receiving difference in fare as a voucher - chat agents say you get the difference back as a voucher if new ticket is cheaper, phone agent says you lose it but maybe can plead your case to a supervisor.
• Required documentation - chat agents just ask for the Dr's office information, phone agent wants that as well but says when you go to use the Flight Credit you'll need to mail them a copy of the test result which would be annoying and (more importantly) time consuming.

I guess much of the above boils down to whether they are truly issuing a Flight Credit per se, or if it's some other method of further restricting the re-use of an existing ticket? If it's simply a Flight Credit, presumably it could just be rebooked online without any agent intervention and so much of the above sounds like nonsense. Any help would be much appreciated!