The idea behind Wake Screen on Crown Up is to use the crown to wake the Watch instead of raising your wrist. While doing so, turning the crown slowly increases the brightness slowly so that in dimly lit surroundings, you don't annoy others. When you've turned the Watch to a (hopefully unobtrusive) satisfactory level you can then raise the Watch while retaining the dim watch face so you can better read it, if need be.
This gives you an option to the Theater mode where it's a tap on the Watch face to see what's what but at full brightness.