I have cancelled a Paramount tv subscription two days ago via AppleID/subscriptions. The option to delete the subscription has been replaced with the message 'if you resubscribe, your ....' how does this mean a refund is in progress?

I have deleted (is that different to cancelled) a Paramount tv subscription two days ago via AppleID/subscriptions.

You will have clicked ‘Cancel Subscription’ to end the subscription, if subscribed through Apple. There is no delete option. (Apps can be deleted. But deleting an app doesn’t cancel the subscription that goes with it.)

How to cancel a subscription from Apple - Apple Support

The option has been replaced with the message 'if you resubscribe, your new subscription will begin on [date] Dec 2022' how does this mean a refund is in progress?

I don’t underhand the December part that you mentioned. Subscriptions normally start on the date that you initiate the start, not months into the future. But the replacement of the Cancel option with Resubscribe options, after canceling, is normal and as intended for any subscription.

Refunds are not automatic from canceling. That is a separate procedure, if you qualify for that. Request a refund for apps or content that you bought from Apple - Apple Support

Did you check the status of your request by following the steps from the mentioned article above?

Check the status of a refund for apps or content that you bought from Apple

Although I canceled my Apple TV Subscription last year, the subscription is still being listed und "Expired" and if I tap in it, I will get the option to resubscribe as well.