Tim,
I would hazard a guess that a big chunk of that extra time was due to the fact that with massive distance gains there are so many drivable, (or at least near reachable), par 4s.
Throw in tricky green surrounds with multiple slopes, angles, and speeds to be dealt with, there is extra grinding and processing on those chips and pitches.
P.S. It was suggested earlier in the thread that longer courses take more time.
As a counter-point to that, a couple of weeks ago the tournament held at Pebble was:
- Only 6900 yards for the weekend rounds, very short by tour standards.
- Limited field event with only the "best" 80 players .
- Completely devoid of amateurs that would slow play with shenanigans and/or crap play.
Yet with near perfect conditions on Sunday, final rounds still took well north of 5 hours.
I guess my relatively simple question about whether it takes longer to walk a 6,800-yard course or a 7,400 yard one didn't sufficiently suggest this, but yes, the "massive distance gains" are at the root of all of this. That it has become necessary to push courses to their breaking point - and that is where The Old Course is to anyone with two eyes - is an existential threat to professional/elite competitive side of golf on multiple fronts, and pace of play is obviously one of them.
Although the best golfers hit an overwhelming number of drives both very far and relatively straight, the fact that they are using hundreds of yards more golf course than they used to makes the dispersion patterns - both one-off and in the aggregate - more varied than when they hit the ball shorter. Bigger dispersion means more time spent not just walking farther downrange to tee shots (and backtracking to and from new tee boxes), but also taking more time to plan the next shot from thick rough, behind trees, along Temporary Immovable Obstructions, etc. If you can't see how this can have a significant effect on pace of play - beyond the "negligible" or "not top three" dismissals you and Erik have proffered, I don't know what to say.
I don't know whether you've played Pinehurst No. 2 and No. 3, but the difference in time taken to play both golf courses is profound. And before you protest that there's a bigger difference in max yardage between the two (7,500 vs. 5,200), consider that a) the difference in par (70/71/72 vs. 68) stretches that number, and b), a large portion of people are playing No. 2 from less than 1,000 yards more than they're playing No. 3, and still the pace of play is a solid hour different.