I'm a little confused, has this person contributed to science in any significant way ? If not why should we listen to this person and ignore scientists who have actually achieved success in their field ?
It's a fair question. But be warned: You're not going to get a much less diverse set of answers from them, though. I would suggest also listening to scientists who established themselves 30+ years ago. You'll likely hear a different story compared to the current crop.
In the 00's, some of my fellow graduate students did more work for their PhD than many faculty members I know did to get tenure in the 80's and early 90's. The high level of work demanded today is mostly due to inbreeding attitudes in academia. It's entirely an internal problem.
source : http://cra.org/crn/wp-content/uploads/sites/7/2017/05/2016-T...
Is 60% pretty high compared to other fields?
Source (for econ at least; CS is anecdotal): http://noahpinionblog.blogspot.com/2013/05/if-you-get-phd-ge...
Looking abstractly at the "market", you are right. Asking a person on a tenure track committee why they're forcing newer hires to do a lot more than they ever had to do to get tenure, and getting that answer, is problematic.
Nothing in the market is forcing the hand of the person on the committee. Nothing. It is the equivalent of "I'm being a nasty jerk because I can." The market helps in him being nasty, but it is his/her choice to be so.
If you look at the daily lives of some of the greatest scientists and creatives in history, you'll find that a surprising number of them have had similarly compressed schedules. Newport's blog discusses many of them.