How he arrived at these numbers I'm not quite sure, but supposedly he did a lot of research and trial and error with the people at Cuisanart to develop his methods. He gives a target mix time of around 45 seconds, with provisions for adjustments. Again, everything is stated very specifically, it not just a matter of throwing things in the food processor and turning it on until it looks OK!.
Of course the temps are very specific, otherwise he wouldn't sell many books. The truth is that there aren't any magic numbers, temperatures, # of revolutions, etc. The specific instructions that he gives will give a certain/specific dough condition. You can arrive at that dough condition numerous ways. Okay so it wouldn't be exactly the Van Over method, but it WILL do just fine.
Consider this....even if you use ice cold water, if you do a 30m to 1hour rest period after mixing the initial ingredients, the dough temp will have approximated room temps during the rest period. So the starting temps can vary quite a bit depending on how hot your kitchen is and how much of a rest period you are using. Same with the finishing dough temps. Once done mixing, if the dough is bulked at room temps, it will approximate that temperature rather quickly. So IMO, it matters not much if the finish dough temp is 75F or 82F. Both doughs will bake up extremely similary.
Getting hung up on dough temps is like getting hung up on NY water. It is just one variable among many. If you don't have the vast majority of your ducks lined up, focusing on dough temps alone or sourcing NY magic water is a waste of time and really just pointless.
DMC, this post is not directed at you so I hope you don't take it that way. I understand what you are saying and I appreciate your post. I'm just merely stating my opinion (ranting).
The FP makes a decent dough, but it's more inherant in the type of mixer and it's action than it is Mr. Van Over's specific methodology. Again, I haven't read the book so maybe I should just keep my mouth shut.