I always felt the tree in the middle of the fairway on Pebble's #18 as well as the tree to the right of the green on #18 was just part of the unique character of that hole and made the hole special. Sure, it might appear to violate some principle of golf architecture but so what? I feel the same way about the trees directly behind the mid-fairway bunkering on #17 CPC that Alister MacKenzie originally did. I even feel the same way about all the trees IN and completely AROUND all that bunkering on the right side of CPC's #18 that MacKenzie originally had.
I think in golf architecture doing stuff like that---eg basically breaking what some think are the "rules" or "principles" of golf architecture is a good thing. It creates that undefinable but necessary "difference" in the art of golf architecure!
It's a bit like the great and unexpected joke---it CAN go over really well just so long as the comedian doesn't repeat it to the same crowd too often!
In a real way this is sort of how I look at the unique architecture of Pete Dye. Pete's unquestionably a great architect in many ways but his penchant for the occasional "offbeat" in architecture sort of put him at the top. How that works and why in the evolution of architecture just may be eternally mysterious---because so much of the "offbeat" in architecture just bombs right out of the box!
It's not just the famous architects either, in my opinion. An example is up to 3-4 holes at a course in Fernandina Beach called Royal Amelia Links that might not even make it. I can't even remember who the architect is---somebody most on here have never heard of though. There're those 3-4 holes down there that are pretty unusual to unique that some might hate or certainly might make some scratch their heads---but you remember them and they create real interest. It just seems like there're ways to play them that although seemingly "offbeat" is nonetheless gratifying in some way. That's generally good enough for me.