Yes, it refers to approval to use taxiway Yankee, which crosses 24S from 24 right. This Taxi way travels "back" in a southeast direction. It is also the first "left" you can make from 24R.
WN will always ask for it, since it will get them back to Terminal 1 the fastest. Also any turbo prop heading to terminal 1 or 2, since they can easily reduce speed fast enough on landing to make Yankee.
Rob