There is no way that the GMPP extended warranty covers more than the CPO:
"The Cadillac Certified Pre-Owned Warranty1 is a true extension of the New Vehicle Bumper-to-Bumper Warranty. It adds an additional 2 years or 20,000 miles to the original factory 4-year/50,000-mile Bumper-to-Bumper Warranty. That’s 6 years or 70,000 miles of worry-free protection1 on every Cadillac Certified Pre-Owned vehicle, whichever comes first."
The CPO would cover trim items that the extended warranty would exclude.
Here is what is excluded from Major Guard GM extended warranty:
Excluded parts and services: If the part or service is not on this list, it’s covered under Major Guard
Batteries
Body parts, panels and rails
Brake drums
Brake pads / linings and brake shoes / rotors
Bumpers
Carpet and upholstery
Chassis frame
Convertible and vinyl tops
Correction of air and water leaks
Cross members
Drive belts
Engine coolant
Engine tune-up
Exhaust component and catalytic converter
Filters
Fluids
Glass
Heater and vacuum hoses
Hinges
Lenses
Light bulbs
Lubricants
Maintenance services and parts required or recommended by the vehicle manufacturer
Manual clutch disc
Paint
Radiator hoses
Recharging the air conditioner
Rust damage
Sealed beams
Sheet metal
Shock absorbers
Spark / glow plugs and wires
Squeaks, rattles, wind noise and odors
Suspension alignment
Tires
Trim, moldings and bright metal
Weather-strips
Wheel balancing
Windshield wiper blades
I bolded some items that ARE covered by the CPO bumper to bumper warranty.