Michael Dugger,
That's a neat picture, one that would seem to present the golfer with a good deal of uncertainty, even with yardage indicators.
But, if a tree or tree top was visible behind the green, wouldn't it still be a "skyline" green ?
Isn't a "skyline" green one that sits above the area of approach, with the terrain behind the green falling off, such that the horizon is the putting surface ?
I often think of the 13th hole at Sand Hills.
If, tomorrow, someone planted a spruce behind that green, wouldn't it retain it's skyline qualities in terms of the spacial relationships of the features, the tee, green and land behind the green ?
Belmont CC outside of Boston has a wonderful uphill skyline green.
I believe it might be the 17th hole. Unfortunately, someone planted evergreens behind the green.
Whether it was to protect golfers on the fairway behind the green or for framing purposes, or both, doesn't matter. A wonderful approach shot was ruined by the introduction of trees. If the trees were removed the green would have an appearance similar to the picture you posted.
Hence, I don't believe that trees behind a green disqualify the green as a "skyline" green. Rather, they merely frustrate the intended use and appearance. .... temporarily.