'Tuna' might not be the best word to describe these fish species served as sushi. In the original Japanese the labeling is much more explicit, where they are called 'maguro' which is less broad a category than 'tuna'. So while escolar may be 'tuna', it's definitely not 'maguro'. In fact escolar has been illegal in Japan for for decades because it's considered harmful due to its diarrhea inducing wax ester content.