1755 A Doritos

Recently I chanced to drive by Taco Bell. I was interested to see signs for their latest epicurean culinary offering. Taco Bell, as their marketing efforts have branded in our brain, is known for "thinking out of the bun," which for me means lots of fun, and fun-sounding, items to talk about. From Chalupas to Volcano Burritos to unfortunate suggestive gut reaction catch-phrases like "Run for the Border" thinking out of the bun has lead to me writing a load of essays featuring Taco Bell.
Their new item got me in a different way. It's their Locos Taco. In case you're living under a rock, Locos Taco features a taco shell made from Doritos. So one could have a taco-flavored Dorito taco.
But actually one couldn't. Because according to Taco Bell, you would have a taco-flavored Doritos Taco. The Dorito would have an S on it. The signs in their windows prove it. They say, "My Doritos is a Taco." "My Taco is a Doritos."
That's right, Doritos with an S is supposedly singular. I've been getting it wrong my whole life. Apparently a Doritos is like a deer or a fish. Or Doritos are like deer or fish. The singular is the plural.
So why no singular Dorito? Taco and Burrito are both singular or plural. And it's not just corn chips. One does not eat a "Ruffles." I don't like it. Is the same to be said for Fritos? I've always been able to enjoy one Frito or, as their ads once said, "Munch a bunch of Fritos, corn chips." The parent company of all three, Ruffles, Fritos and Doritos is called Frito-Lay, both singular, so I'm still confused.
Am I now expected to eat a potato chip, or a potatoes chip?
America, ya gotta love it.