I measured it for my book using lab-grade equipment; it was about 0.3 to 0.35. But I was measuring distilled water, not mash. I think AJ was suggesting that it might be less of a difference that way. I'd like to try some experiments with different liquids and see if it makes a difference.
If you're talking about a 0.05 difference, you also have to look at the precision of your instrument. Can it resolve to that level? How is it rated?
Also, you say "mash temps". It's a curve, so the difference isn't the same across all mash temperatures. I'd have to go back to check my data to see where it was 0.3 and where it was 0.35, but it was likely in single infusion ranges.
A 0.05 difference in pH isn't going to affect your beer in any meaningful way, so I don't know that it's worth arguing about.