Yes, I know, iPadOS has scribble effect, but that is meant for single line input, not full feature note taking.
More importantly, the Apple Pencil could be a much more natural highlighting solution. Much like reading a book, I see using your fingers to swipe/scroll and the pen to highlight/underline. Instead of the press>hold>slide motion, the pencil would just begin highlighting on first contact.
A long press with the pencil creates a note, while a long press with a finger launches a search.
Right now the Apple Pencil is still just a glorified stylus.