It actually started off without one, but then it looked like a second theme category with a ‘components’ tag, so the hyphen was popped back in to be more visually intuitive:
I wanted to give them equal parity with plugins and full themes, as well as provide two separate lists without the topics being mixed together.
Yup. 
Or make the new one singular. As per:
From a descriptive point of view I still think plural sounds more apt (it’s a list of theme components after all), but prior style counts so singular could still win out. 