This is what I was thinking, which led me to think he's over sparging. But he did say that he took temperature readings of 175F+.
If you're batch sparging with water that's 180*+, it'll raise the temp of the grain bed, so I doubt your run-off is actually over 170*F.
Ok so how do I stop "oversparging".... try to balance my first run-off and 2nd run-off?
For instance on the Altbier I'm drinking right now, which got me thinking about this, I ran off 6.0 gal, then sparged to collect another 11.5gal to reach 17.5 gal, which I needed because I wanted to do a 75 minute boil.... I guess that is pretty unbalanced, and I could mash a lot thinner to get that balanced out (I doughed-in at 1.5 qts/lbs, then did an step infusion to get my sach rest, this left the mash at 2.15 qts/lbs, then I did a decoction mashout).
My 2012 Oktoberfest was more balanced in the run-offs; I collected 7 gal first, then sparged 9 gal more to get 16 gal total which is all I needed for a 60min boil. Still had a mildly unpleasant astrigency about it....