This sounds like a chat person talking nonsense, whch is more common than it should be. Very likely just confused with their All Access offering.I literally got him to confirm this 3 times to make sure I had it right (only a technical support dude after all... ) Because for me, £449 + £24.99 (for 2 years of GPU) = £473.99 is a substantial saving. But he seemed adamant that this was a thing and would be announced soon (when pre orders go live perhaps?).
You're not going to get 24 months for £24.99 (=£1.04p month). A pack-in code or a redeemable option baked into the console for a 1-3 month XGPU sub is feasible though.