Your refund experience with Amex was clearly poor, but does not fit in with my own experience prior to these difficult times.
I have had to claim refunds from Amex several times in the past year or so, particularly with Avis. I have done this online, using the facility there, and the costs being claimed back have been removed from my account (into a separate column) until the matters were resolved. Amex give 6 weeks for this. In all those instances the retailer/service provider did not answer Amex satisfactorily and I never had to pay.
My guess is that the chat lines have had to be manned by staff not properly trained, as you have intimated, and that ultimately Amex have been overwhelmed by the claims from all around the world.
