No, they don't stand by that.

Flex tickets (on shorthaul anyway) don't allow refunds after a no-show; only for a rebooking.

If you're working on a strategy whereby you will only be in a position to attempt cancelling a flight in the dying minutes before checkin closes - at a time when you are presumably under some pressure/stress and may not be able to contact the correct person on the correct number in sufficent time - I would advise you to consider if there aren't any other better options for whatever kind of fall-back position you are working on.

I'm a great advocate in planning pessimistically. But instead of buying unnecessarily expensive (Flex is expensive) tickets, I usually have a different strategy, involving cheaper, intentional throw-away tickets. I'd book a backup throwaway ticket that would assist me in case of whatever misconnect or other worry you are may be attempting to address. Such a throwaway ticket, which although not refundable, can usually have the taxes refunded. If booked sufficiently cleverly and long enough in advance - and on any cheap carrier - it's a better insurance policy than betting on being able to put yourself in a position where you have enough time to cancel this unnecessarily expensive Flex ticket.