Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Just saw the same thing in Apple Mail. I don't know, but I appreciate that you asked the question. I think the right question is if there is some way to tell what apps support split view. A list of supported apps would be great.
 
When I select the application to appear on the furthest left, all the running apps that offer Split View open up in the right-hand side in a Mission Control-type view. You can then mouse over a window, and it will tell you whether that app supports Split View.

TextWrangler doesn't, which is annoying. It would be nice to have TW and Terminal on the screen. It would be nice to have one on top of the other (so that there's a top half and a bottom half, not a left half and a right half).
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.