The WP cars and PO cars aren’t exactly the same. WP cars come in a pack, are pre-tuned and are ment for new players to have a good car in a diverse racing setup (road, off-road and cross country as well as some A, S1 and S2 class). Basically the WP cars will get you very far in the game. We had a WP pack added to FH4 long after it launched but Mike Brown back then mentioned in the accompanied Series update that the WP cars were ment for new players.It would seem these have taken the place of pre-order cars?
PO cars are similar and are also pre-tuned but they don’t come in a pack, each one of them was exclusive for a specific retailer when you purchased FH4 there (GameStop, Target, Amazon, Xbox, etc…). It’s been mentioned by Playground Games already that FH5 won’t have any PO cars anymore. Which IMO is a good thing, all cars should be accessible by all players without having to revert to EBay and such to get the codes for missing PO cars.
The only car that comes close to what the PO cars were is the 1932 Ford Coupe FE, which is an exclusive car for the FH5 controller.