Do you really have someone who would be equally comfortable/effective with a large complex PWA, on the scale of, say, Trello - and with a beautiful boutique site (say, for a sophisticated web-native publisher), with lots of motion, infographics, video, layers, custom interaction, heavy photography, etc. I've yet to meet such a person. Of course I agree that one can specialize in one and be passable at the other, but to be equally strong in both, I also wonder what sort of career or company produces that...
Not equally comfortable. I think people will always have strengths in some areas over others. But good enough with the weaker skill that they might be preferable over another candidate whose specialism was that skill.
I also think that while in some cases the projects requiring these skillsets are distinct from each other, there are plenty of projects that require both. Consider Google Photo's infinite scroll feature for example.
