I recently found that I can hit some fairly decent shots with a half swing (i.e., from the 9 o'clock backswing to the 3 o'clock throughswing). I also found that my arms relaxed more on the backswing, because I had to set the wrists EARLIER to get the club in the "L" shape at the 9 o'clock position at chest height. Doing this allowed me to hit my approach wedge MUCH farther and cleaner than my old, full approach wedge swing. This got me asking why.
My tendency has always been to set the wrists late and, sometimes, past 90 degrees, near the top of the swing, and this means the club stays "heavy" well into the backswing, which means it's harder to keep the club on plane (the arms remain more tense as a compensation). Every adjustment to the swing (as Hank Haney says) is "action and reaction": When you make a particular change it can have effects beyond that particular change. In other words, changes to your usual setup or backswing can affect what follows, and vice versa.
In this case, working to set the wrists earlier (at 9 o'clock and at no more than 90 degrees) makes the club lighter going up, because it's balanced when in a vertical position (when the club is straight up and down, its weight on the hands and arms is negated). This makes it easier to keep the club on plane into the backswing and it relieves tension in the arms. And since the body works to make the throughswing a mirror image of the backswing ("L" shape to reversed "L" shape), it helps keep the club on plane coming down and assists with timing and dynamics.
So another benefit is that hitting half shots can be great for reestablishing your rhythm and timing.
Some professionals either set the wrists late, set them beyond 90 degrees, or both. But if you're like me, you're not a pro. You don't have the skills, talent, and timing of a professional golfer. I think any amateur would have more consistent results setting the wrists earlier (no later than the time the hands reach chest height) and only to 90 degrees (the "L" shape).
This line of thinking mirrors the Ernie Els lesson I've posted on earlier about "keeping the box" (another way of looking at the "L" shape). Even though Ernie DEFINITELY sets his wrists early as I'm advocating here (he sets by waist height even with the driver), he was primarily referring to keeping that shape on the downswing--a step critical for power and hitting inside-out. Again, some pros can set the wrists late and keep that box or L-shape coming back down, because they've spent the time honing that skill to maximize distance. I think most of us would do better to copy the backswing motion of Ernie Els, Ian Poulter, or Nick Faldo by setting the wrists early. Most professionals these days set their wrists, at least, by the time their left arm is horizontal to the ground (a mid-backswing set); professionals of bygone eras typically set their wrists late, near the top (a move often associated "float loading" the wrists at the top).
Setting the wrists to 90 degrees earlier doesn't negate a float load feeling in the wrists at the top. You should still let the weight of the club fully cock the wrists at the top to get maximum power.
Like most theories in golf, there are detractors and protractors (i.e., authorities for and against) this line of thinking. Some instructors advocate setting even earlier--right off the ball. You need to try it for yourself to see if it works for you; if you're suddenly hitting the ball better by setting your wrists earlier, who's going to tell you you're wrong for doing it?
My preference is to set the wrists early to 90 degrees when the club is around waist height. The left arm rolls very slightly also (see video below), such that the club is parallel to the target line during the takeaway and the wrists already have their maximum set. Stopping the arms and club at chest height will result in a half swing, which might be all you need for your wedge approaches. From that point onward, any continued movement (from a half swing) is all shoulder movement to the top. The wrists don't need to set or bend any further, as you might see with players like John Daly or Bubba Watson; remember that they're pros--you aren't. Going beyond 90-degrees in a float-loading type of backswing requires impeccable timing and skill to harness the extra power and lag while maintaining consistency.
For the better part of 20 years, ever since the reconstruction of my swing in the mid-1980s, I have focused on this halfway-back position via what's become known as an 'early wrist set'. It's quite simple: I look for my wrists to be fully hinged and the club 'set' up on a good plane by the time my left arm is at horizontal.
...The beauty of working on this halfway-back position is that all the details of a technically sound swing are encapsulated within it: you have a full wrist hinge, the club is swinging up on plane, and you maintain good body angles. Completing your shoulder turn gets you to the top, whereupon unwinding the body invites the hands and arms into the perfect hitting position.
One way I help myself get into a better position is to hinge my wrists early in the backswing. I do it as soon as I take the club back, rather than waiting until I'm nearly at the top of the swing like many golfers do. The early hinge gives me a nice feeling that the clubshaft is pointing where it should at the top. It's one less thing to worry about when I have to put it in the fairway.