How many of those lines of code would have benefited from being able to express that type constraint, if the language made it possible?

You have no idea, and nor does anyone else. But that's what you would need "factual and objective" evidence about to support the claim you made.

By your argument, anything that programming languages don't currently support, must be an "esoteric limitation" because billions if not trillions of lines of code have been written without it. Which would mean programming languages would never add new features at all. But it's certainly "factual and objective" that programming languages add new features all the time. Maybe this is another feature that at some point a language will add, and programmers will find it useful. You don't even seem to be considering such a possibility.