Yes, sight reading is a misnomer because at some level it is almost impossible to sight read a complex piece. It is not like reading a book where you will be able to read the words correctly as long as you're literate. What you can say is that you're familiar with simple/medium complexity rhythms so you can play them as you read.
Not sure i agree with that. I can sight read through just about any piece, albeit not at full speed. If I make a mistake, I keep going. Jazz is definitely the hardest, due to rhythm and complex chords.
As a piano player that primarily sight reads, I end playing a lot of music, so maybe it is partly memorizing patterns.
Jazz is...different. The Real Book is full of mistakes by some Berklee students in the 1970s. Standards as played on the bandstand are very different than what is on the records. The records are all different from each other. The melody is simplified or shortened or embellished, and the chords? Forget it, you'll find out that the piano player likes to play a dominant instead of minor only when you're actually playing the tune. Ask a pro how to think about the harmony of a standard, and they'll explain how they think about the harmony of the variant they prefer.
