Code P00B7

Car runs fine, no misfires, no overheating, no continuous radiator fans, good heat, no leaks.

got a CEL for code P00B7, took it to dealer and they said it has a warped cylinder head and will cost $3,200.00.

the water pump and thermostat assembly was replaced last year for a recall, it is not losing a drop of coolant and has never once overheated.
there is no fluid mixing either antifreeze in oil or vice versa.

i reset the light have gone around twenty miles with no return yet of the light.

would a warped head cause massive loss of coolant, smoking and overheating?
the dealer literally had the car for under an hour when they came up with their diagnosis which I do not think is enough time to diagnose a perfectly good running engine with a bad/warped head.