I've had this also on other versions, don't know when exactly as I haven't had a multiple monitor setup with each OSX version 
I know I can try it myself, but I'm not planning on running a beta OS on my production machine. Maybe someone else can confirm the behaviour has changed or if it's still the same.
I know I can try it myself, but I'm not planning on running a beta OS on my production machine. Maybe someone else can confirm the behaviour has changed or if it's still the same.