10. Right, yellowtail is easy to tell from 'tuna.'
But, there are different kinds of tuna that look like maguro to the inexperienced eye, or even the somewhat experienced eye. Inexperienced sushi eaters don't know this. So they may get 'tuna' but it is less and less often blue fin and more and more often one of a few others like big eye, yellow fin, etc. Because of the Japanese situation (mostly) with 'tuna' there is little blue fin left and the price is astronomical.
And unless one knows sushi, it can be difficult to tell the difference between a number of white fish --fluke, sea bass, red snapper, etc...
Most people also don't know the different cuts/quality of toro. etc..