Very common, get it levelled at your local machine shop.
I didn't question it as it just cost me $40 and it kept me at peace knowing that once I finished my headgasket I wouldn't have to worry about it being warped.
I have tons of writeups about changing the headgasket that do mention getting a straight-edge ruler, and at the time I was in high school my instructor for automotive told me just to take it to get it machined anyway.