Which is best premium CPO SUV to buy

It used to be, but now it’s extremely limited.

Their own language straight from their website says

12-month, unlimited mile warranty, upgradeable for an additonal 5 years*** covering replacement or repair of defective components within the following systems: engine, transmission, drive axle (front and rear), steering, suspension, brakes, electrical, air conditioning

That leaves out so many of the common failure points of a modern car, things that can throw a CEL or leave you stranded. Just off of the top of my head

Turbo and super chargers + related parts
Radiator and cooling system
Ignition, alternator, starter etc
All the sensors (O2, MAF, EGR, etc)
Gaskets & seals
Manifolds
Infotainment & displays
ACC, BSM, AEB, FCW, RCTA, LKAS or any other aspect of a modern safety suite
Headlights
Sun or moonroof
48v or PHEV systems etc etc if applicable

Between parts and labor a lot of these can be very expensive to fix on a late model luxury car