Since you're getting different results I went back over all the data entry in the spreadsheet and found my error. In v10 I had linked the Mash/Sparge water volumes from the Water Adjustment tab to the Mash Acidification tab. v10 gave me an unadjusted pH of 5.3.
When I input everything into v12 I didn't link those cells so the mash water volume was correct on the Water adjustment tab but not on the Mash Acidification tab. When I fixed that my results came into line with what you posted (and with what I experienced).
So I withdraw my previous comment. Bru'n Water v12 was very accurate for this batch. It was user error
Thanks Martin for taking the time to look at my data.