Without the bunker, the play would be to cut off the inside of the dogleg without thought. With the bunker there, the strategy is to drive as close to the bunker as possible without going in. From the tee, the golfer also considers driving away from the bunker to avoid the penalty of hitting from the waste area on the second shot. The angle as well as the distance is better from the left, close to the bunker.
The geometry of the dogleg definitely has something to do with the decision. The hazard is not perfect either, and if it had the shape you describe it would be more effective. However, the bunker forces the player to make a decision from the tee: do I want to challenge the bunker to get a better shot into the green, or should play safely away from it to sacrifice distance and angle? The distance decision is important, because with certain hole locations the player will have a better angle from 175 than from 140.
What you are describing here is much more closer to a penal setup than a strategic setup, in my estimation of the situation. The strategy you're describing is very one-dimensional and you're even admitting that the bunker is only a factor if the player plays more to the left. The fact that you and Joe can have such varied results without the direct influence of the bunker tells me there are options to consider outside of how close to the bunker one is willing to play. Would a ball hit somewhere in the 35 yards between yours and Joe's shot but along a line 10 yards further to the right find more advantage or less advantage relative to both positions? I can infer with geometry that I can play away from the hazard and have a shot of 150 from an ideal angle based simply on these descriptions. For a better player this can amount to nothing more than a 3wood and 9iron that comes nowhere near the bunker. However, with your distance limitations you were forced to take on the hazard to get closer to the hole. This is similar to a player with distance limitations being much more concerned with a 180 yard carry than a player without those limitations.... see my point?
That sort of wiggle room is the criticism Robert Deruntz was applying to the golf course. There seems to be a large amount of space in the fairway not influenced by the bunker in which players can gain similar advantages to the ones earned by you and Joe with your selected lines.
Whether or not this shot 10 yards away from the hazard would find an advantage depends on the pin position. If the pin was on the far right part of the green, my drive would be in a better position. In general, a tee shot of one exact distance will gain an advantage by choosing a line closest to the bunker. It's also one of those strange holes where the shorter hitter off the tee will have a better angle into the green if he hugs the bunker. A longer hitter will have a shorter shot in but will have a poorer angle.
To my mind, the left tree line serves no strategic purpose on the 4th. Even if the trees were not there, only the longest of hitters could carry the waste bunker. Even then, it would be useless to do so because such a tee shot would scoot through the other side of the fairway and leave an awkward angle.
Additionally, the terrain in the fairway is quite interesting. The 4th has a reverse camber fairway, meaning the golfer has to hit a controlled draw to find the spot from which to approach the green. A good deal of thought is required before playing the 4th. A golfer cannot simply blast away and assume he will get a good angle into the green.
Besides all of this talk about the strategy of the tee shot, the green at the 4th is quite good, providing an out for the weaker player and reasonable rewards and punishments for the bold. I'm a fan of the 4th, though it's not my favorite hole on the course.