I'd divide it as essentially "User of Packages" vs. "Writer of Packages", and of course, the dichotomy is not actually a clear one. But the choice was to suggest that there are some people for whom the programming language and its libraries are not an end of itself, and "Just crack it open and write your own thing for X..." is essentially a non-starter.

I think it's useful to distinguish between the two groups, because not only do they have different skill sets, but they have different motivations. For example I will never directly be evaluated on the performance or style of my code in the way a programmer might be - only the paper that code helped me write.