I don't think that was the concern. John is concerned whether his X-plan discount applies to the current negotiated price (based on MY22), or whether it only applies to the invoice price of his actual MY23 vehicle.If he accepted payment from you in return for an order with a specified guaranteed price and does not plan to honor that guarantee [emphasis mine]
JohnSC has a 'guaranteed' price based on the 22MY pricing - but it sounds like this doesn't include the X-Plan discount. If X-plan pricing is based on factory invoice of the actual vehicle purchased, the X-plan discount may not apply to the price JohnSC has already negotiated with the dealer.
So it comes down to whether the 22MY price John has locked in without X-plan pricing will be a better deal than MY23 pricing with X-plan pricing.