Truly a beautiful route. It's hard not to stumble on something amazing in Yosemite. The valley is just the beginning. That being said if I ever hike this route I would definitely slow it down quite a bit. They author rushed a bit too much for my taste. Not to mention planning for 18 miles with 8,500 ft elevation gain on the first day is a HORRIBLE idea. Seriously, for anyone reading unless you've been training hard for a while at high elevation never ever do that. Even splitting that amount in two is a bit of a stretch. This is a great way to either become very dehydrated or injure yourself. Start with 2-3 miles a day and then increase from there. If you're first leg has to be huge camp out a bit around the start and go on a day hike the day before.
I definitely agree that the speed they did it would be too much for me. However, if you hike similar amounts regularly, I think you could easily start with a 10-mile day. I probably would plan with starting at about 7 miles a day, then ramping up to a final pace of 15 or so miles per day.
Yeah, I guess what I'm saying is more aimed at inexperienced hikers who read this and then think they're ready to do it. Anybody who hikes regularly usually knows their own bounds and will never listen to a guy like me :)