I queried this with Porsche UK based on the old pricing, but which had exactly the same wording about PDK oil, and their response (dated 29 July) follows:
I can confirm that the fixed price of £950 for 4 year/40,000 mile service does not include the cost to drain and refill transmission oil plus filter change. Your preferred Porsche Centre will be able to confirm the additional cost.
We acknowledge that this isn’t necessarily clear on the attached. Thank you for bring this to our attention, the page will be amended very shortly.