TR,
Good point. However to me wins aren't the main measure of success for a pitcher for just the reasons you state. I always wanted to win and was almost always on winning teams but I also knew when I pitched a good game and when I pitched poorly, win or lose. Of course, being a pitcher I gave myself credit for a poorly pitched win because I hung in there but I didn't get down on myself for a 1-0 loss unless I did something stupid to give up the run or unless I actually tightened up at some point because of the close score. I certainly made some mistakes in tight situations but I don't ever remember getting tight on the mound. I got tight at the plate a few times but never on the mound.
As an example, I was 4-0 in legion ball and I pitched reasonably well. However, having a 4th round pick throwing in front of me and a future big leaguer throwing behind me each game didn't hurt my chances for getting wins. Neither did having a 2nd round pick at SS. I was much more impressed with posting a 0.00 ERA although in hindsight being a relatively soft throwing righty following a hard throwing lefty probably had a lot to do with that.
With my 14yo's I've seen kids go from having the "appearance" one game and not having it the next and usually the difference was the quality of the opponent.
On the other hand I've seen my son have the "appearance" when he was facing top competition that was out of his league and I've seen him not have it other times against less strong competition. Looking through my rose colored glasses he has the "appearance" more often than not but it isn't there 100% of the time. The same goes for my other pitchers especially now, just having moved into 14u, throwing from 60'6" and finding out that their fastballs no longer get by even the average hitters on good teams. Time to learn how to pitch.
Some of my softer throwers are showing more confidence because their stuff has become more effective with the increased distance.