The only way it's a problem is they keep adding other stuff such as a banana ice cream Sunday.
Chocolate and vanilla soft serve twist is a thing, a glorious, glorious thing.
https://www.google.com/search?q=vanilla+and+chocolate+soft+s...
You can see it, wish it, present it, however you like, but soft serve is ice cream, that is a fact, and mixing vanilla and chocolate ice-cream does not fail, also a fact, or it would not have survived for more than 60 years[0].
You still don't have to like it.
Additionally, thank you for entertaining such trivial matters with a passion. I have been amused.
[0] http://www.albertleatribune.com/2001/06/column-hes-the-man-w...
And either way, the challenge would allow chocolate topping to a vanilla icecream base, or chunks of chocolate in a vanilla ice cream. Both of which are extraordinarily common.
The only ice cream my granfather would buy was neapolitan, aka choc-van-straw.
Soft serve is still a type of ice cream, at any rate, and I sell a lot more twists than I do chocolate cones at my fast food restaurant. Black and white shakes are also popular. I'm a huge sucker for vanilla soft serve with chocolate syrup drizzled on top. Lots of vanilla+chocolate+ice cream possibilities!
(If you insist, the argument: butterfat is measured by volume and soft serve by default has less because it's aerated a lot more than what you consider to be ice cream. we also have low-fat ice cream but it's still called ice cream. and what do you call gelato if you think butterfat is what defines "ice cream"?)
Please just try this experiment: take a scoop of chocolate and a scoop of vanilla ice creams and mix them together and eat it. Is it unpalatably overly vanilla? No, of course not, it tastes like mildly chocolatey ice cream. Which is to say, it's pretty good.
I'll admit that I'm interested in what contortions you can come up with next to keep justifying this. I'm greatly amused by this conversation.
You can try the same thing what cheaper ingredients by adding the same fairly large quantity of vanilla extract to unflavored ice cream and chocolate ice cream. But, you miss out on some of that strong cream flavor.
PS: Even just good chocolate is hard to find in the US. Hint it has zero wax content and a short shelf life.
On the other hand, I commend you on being completely consistent and somehow going through with this conversation without a hint of sarcasm, snark or anything other than a deep passion for the subject. More than I can say for myself. But I'll still hold this as perhaps the most surreal exchange I've ever had and can't quite remove the feeling that this was a masterfully executed joke.
[0] https://www.google.com/amp/www.foodnetwork.com/recipes/alton...