When talking to a painter, would you tell him he'd have no problems with sculpting?
Learning a new language or specifics to a new domain is similar to an artist who primarily deals with pencil and ink, learning how to paint (or vice-versa). This is what most of the other answers are talking about, how your friend is partially correct - a lot of the same concepts apply.
But teaching a painter how to sculpt a 3D object, or write a novel (Both forms of artistic expression) is a different beast entirely. That's the viewpoint you're coming from.
Web-based software requires an entirely different type of thinking than desktop software. Both are completely different when applied to games versus a work environment. I suspect working on an OS or integrated systems also require thinking a different way (but I have no experience with them). And I have no doubt there are other domains that also require a different way of thinking.
Summary and examples:
"Art" includes sculptures, novels, comics, and paintings. Skill overlaps include:
- Body form and color theory: Sculptures, comics, and paintings
- Textual communication: Novels and comics
... And so on. But as mentioned above, a comic artist is unlikely to do well on their first novel. They need to think differently.
Likewise, there is overlap in different fields of programming/software engineering, but most of them are too distinct to be able to just jump in. For example:
- Algorithms: OS/integrated systems, games, and other places you often need to optimize for speed or memory. Rarely a big deal in web development
- Design: Everywhere in web development, but not very important in integrated systems without a UI.
- Client/server software: The "don't trust the client" mentality, which doesn't necessarily exist in some domains (single-player games and other standalone desktop software, which I admit is rarer these days).