Yes, he gets his own category because he has earned his own category. His music is beautiful and complicated and everyone will tell you to never give an accompanist a Sondheim song to sight-read but sometimes directors will ask for it and sometimes it’s worth the risk to look seriously impressive.
Anyone can Whistle from Anyone Can Whistle
I Feel Pretty from West Side Story
I Know Things Now from Into the Woods
On the Steps of the Palace From Into the Woods