Record sketch was always there. But, it was only available if you started with one specific note template (I can't remember which one).
I think if you record a sketch, save it, then open it back up, you'll see how to play it back.
What's it for? Here's one use that comes to mind: Imagine you're in class and your teacher draws, say, a methane molecule on the board. Then they erase part and draw some more and and now announce that this is a hexane molecule. You're taking notes and you've drawn the first one. You want that to be kept in your notes. But, you want to make a note of hexane, too. Do you start a new page and draw the whole hexane from scratch? Or do you have recording on and just erase and draw new, just like the teacher did? If you do the latter, then you can replay the sketch later and see both drawings, as the playback proceeds. Just one idea...