Ryan,
Not sure exactly what you mean, but think I do.
A few things cause standardized clearing -
First, it usually matches the width of the irrigation system, whether 2,3, or 4 row.
Second, the clearing is often marked by the contractor and not the gca, and they tend to straighten the lines. When I did Avocet at Wild Wing, the Owner commented on how my clearing lines were the most artistic, free form and curving, rather than a straight line 125-150' either side of center. Those gently curving lines takes some time and also drive irrigation guys nuts, since its sometimes harder to fit the sprinklers in irregular spaces.
I also try to leave "lone soldiers" or small clumps within the clearing to soften the edge and break it up. However, I find that I need to leave them to accentuate points of the clearing that are jutting into the fw. If I put them where the basic tree line juts out, it effectively just straightens the line right back out.
Lastly, I think some folks do too tight a curve - you can only have two or three curves per fw. I know this sounds forumulaic, but I have found that the curved edges of clearing look best when the jut out at about a 7:1 ratio, i.e. over 210 feet of length along the fw, the "outie" goes back about 30' and then comes in in about another 210 feet.
Like everything else, it must be fitted to the land. I have often flagged an entire fw, and got to the end to see a tree I think I can feature, and then reflag it accordingly.
Not sure that answers your question but hope its a start anyway.