People at feed stores often have no clue as to what is what with chicks. and they will often mix the breeds together when stocks start getting low.
Hoover's doesn't have the greatest reputation, either, but this is clearly their fault.
You are right to be suspicious. The head spots indicate the chicks will be barred, and only male Midnight Majesty chickens are barred. It's how the hatcheries can tell females from males at birth. It's possible you got some other breed, but I don't think you have Midnight Majesty Marans females...