There are people who deliver code as their product. For example, a library developer's product is code. But it's rarely a single line of code – it's more like an entire function, class, or set of classes. You might measure something like "Number of fully-tested public API functions released for use by programmers" for a library developer.
You'd probably have to do something to count new features for existing functions in that case, too, like counting every new feature for a function that improves its API as being a whole new "function" delivered. Of course, since the original metric says "fully tested," any new feature would have to be fully tested as well, to count.
But however you choose to measure it, the point here is that even for the small number of people whose product is code, you're measuring the product.