I think your math is about right Scott. Personally, I like the idea that even a shorter hitter has to think and be challenged a bit off the tee on occasion. It's not so penal as to be impossible...as you can see from the picture, the fairway is mowed nicely to the left of the bunker, giving the short hitter, if they choose, a path around the bunker. I like the fact that the bunker sits at an angle from the tee, making it easier to clear the left side than the right side. As it's positioned, it strongly encourages the short hitter to aim over the left half of the bunker, or just to the left of the bunker...this angle (by pushing the short hitter left) actually helps the weaker golfer, as this green is far more receptive if approached from the left side. Without the bunker, the weaker player might aim down the middle and be surprised by the right cant of the fairway, which would push their ball right and thus force a far more difficult second shot.
Even good golfers aim at the left edge of the green here, since a wayward shot is penalized so heavily with the trees. So for me, the bunker adds a strong visual element for good golfers, and interesting options (with an heroic carry) for the shorter golfer that might actually help set up their second shot. I've watched players of all abilities, women, seniors play this hole, and it poses a strong challenge with a lot of interest for all of them...it's also a great example of how MacKenzie liked 1/2 par holes. This isn't really a par three, it's a par 3 1/2, with a green complex so challenging that even a short hitter who "lays up" has a sporting chance in a match against a longer hitter golfer who goes for the green.
Scott, I should note that this hole was actually about 240 yards long when the course opened, and has been shortened over the decades...there's still a debate as to whether the club should push the tee area back to fully "restore" it. So at 240, that cross bunker comes into play even more for the average golfer, and as originally designed it might make more sense to you even if you don't agree with my analysis of the hole as it is today.
Rob