And you'll learn that over time, when you create variants on the fly and then delete them to satisfy primal urges like this, down the road, your chances of doing some meaningful analytics become diminished.
Here today, gone tomorrow is a regular pattern for some. A variant sells, money is in the bank, move on, who cares, see ya, so long, thanks for the fish. But for those that have to track what happens to inventory, when, and for how much (I hear this is a common thing)... deleted one-time use variants spell absolute disaster. You lose the ability to easily figure out "hey, what's this XYZ thing we sold for $189 last February 11 to Joe Schmo?"
So ya, it is obvious you can do this, but it is less obvious if you should do this.
It is also pretty scary to think you used the Ajax API to create a variant. That has be implied that you used the Shopify API since the Ajax API has no permissions to do such a thing. And if you did use the Shopify API to create a variant, using Ajax, and it was a customer session that ran that code, it means your shop is terribly compromised and not secure at all. Your API token is available for the public to use as they see fit on your store. I can go there right now and create a variant on the fly for 0.01 and have it shipped to me? Yay! Early Christmas.