It wouldn't surprise me if it was. I read in some other places on here of people explaining the same things. I wonder is you could take you car to advance and see if they can read your coolant temp. with their scanner? That way you'll know for sure and it'll be peace of mind just knowing the needle is off and high.
I know someone mentioned on here about taking the gauge cluster apart when the cars cold and moving the needle for the gauge. And I know there companies that calibrate dash clusters etc. Personally myself I dont care now, I know it reads 11-13 degress high and theres no problem, so I wont be trying either of those solutions! Plus, I hope to not have the car much longer as Im really looking for a GXP!
Good luck.