Maybe they got the names mixed up? Six fishes in Ebonheart has Eight plates displayed on a hutch. I havent been to Eight plates in a while but I bet they have a lot of scales lying around.

I think it's just a coincidence. There's one at the Halfway Tavern in Pelagiad that also has eight plates.

Err... I don't think it they were literal plates... Unless the Lizard's head is anything to go by, that is.

The "8 plates" sign is just an indication of an eatery/tavern in the game. Though choosing to name one "Eight Plates" does confuse things a bit.

By the way, there are sign mods that add individual business signs, and do a very good job of it, too.