The trees were there from the outset, and surrounded by bunkers. When, or more importantly, why they were removed I do not know.
It's one of the more inspiring tee shots ever, made less interesting by the most recent 30-50 yards of technology. For some the hole loses something, while others might gain something.
Without this distance, the clump of trees/bunkers serve a strategic purpose in that they force a distinct decision off the tee.....bold versus safe, short versus long, wind direction for approach...etc.
I agree with the comment on the rear bunker....but it was always that way and MacKenzie did what we might call a "respectable" job out there. The original bunkering scheme on 17 was more dramatic than today's version, in which case the opinion might differ. But hey.......when you put Fazio to work on a classic, one can normally expect either blatant or subtle abortions.
To answer the original question, a copse of trees with ample width is acceptable and can be a turn on. CPC #17 fits this description, as did #12 Stanford at one time.