If I were designing an organization with such a division of labor, those wouldn't be different job descriptions but different activities within a single job description; maybe I'd spend 22 days a month doing product-engineer stuff like adding features, and 3 days a month doing support-engineer stuff like visiting customer sites, diagnosing customer problems, and answering calls, while maybe hatchnyc would prefer to spend 22 days a month doing support-engineer stuff and 3 days a month doing product-engineer stuff. The reason is that, doing either activity, you gain an enormous amount of knowledge that's crucial to the other activity, but very difficult to even put into words, much less into a knowledge base.
Bill Gates found it useful to answer tech support calls as late as 01989: https://www.entrepreneur.com/article/289857
This is good, but it's easier when you're a very extraordinary human, and your own boss!