In terms of texture and taste, white tuna may very well be indistinguishable from escolar for a lot of people. It's still much less desirable than white tuna. Japan has banned escolar in 1977, deeming it toxic.
Oh, yes. Yes indeed. Escolar is quite tasty - I've had it deliberately - but the gastrointestinal side effects can be very nasty. You don't want to go there when you think you're just eating tuna. This is a very underhanded substitution for a supplier or restaurant to make.
In terms of texture and taste, white tuna may very well be indistinguishable from escolar for a lot of people. It's still much less desirable than white tuna. Japan has banned escolar in 1977, deeming it toxic.