Highest Mash Extraction Hit via Single Batch Sparge?

I usually hit 79% consistently. Some batch's have varied + or - 3% and that seems to generally be due to mash thickness / grain bill size. This past weekend I was astonished to see that I hit 89% mash extraction and am trying to wrap my head around why / how it happened.

NOTE: My refractometer was calibrated and I did multiple measurements.

There were a few variables that made this brew day different:
1. thinner mash than usual
2. extended mash time (90 min for saison vs. my usual 60 min)
3. didn't do a mash out (only hit 160F after batch sparging, so it really just extended my mash to 100 minutes)
4. used some lactic acid for the first time and brought my mash ph down to 5.3 - based on ez water calc's, not a test meter (it's usually around 5.45 - based on ez water calc's - not a test meter), etc.

Now I can see how all of those could contribute to an increase, but I still am scratching my head because it just doesn't seem possible to hit 89% mash extraction with a single batch sparge. Maybe that is where I'm wrong. Maybe it's quite possible and just not common? So I'm wondering if anybody else has ever (or regularly) hit the upper 80's with a single batch sparge?

 

This particular mash was most of those those things.

34.5 pounds of grain in a 19 gallon batch
11.6% wheat (wouldn't call that wheat heavy though)
1.913 quarts per gallon mash (much thinner than my usual 1.5)
147F mash (quite beta favoring)

Typically beta temp favoring mashes extract better than alpha temp favoring, although I've read Kai T's studies that claim 152F will extract even better than lower temps.