Why would you need to change your ticket back into Classic?

I cannot really understand why one would need to update a ticket from Classic to Flex, either, as both tickets allow changes but it is self-evident that a Classic to Flex ticket cannot be refunded – if it could, it would in practice make all tickets fully refundable, which does not make sense.

I can't see how you could dispute anything here. But you can of course change your flight times within PE Flex as long as you pay the fare diffrence if there is any.