Funny this would come up. I just saw a place advertising 'cod & chips'.
One, I think it was to make you notice. When they switch things up, you're more likely to notice.
Two, a nearby restaurant serves perch as their fish and chips dinner. So, they're advertising a better choice for somes tastebuds.
I like them both. It's the batter that matters, and honestly, I'd love to eat it every Friday night but my stomach can't handle that deep fried stuff.