That's some interesting stuff. It's compensating for the strings going a bit sharp when you play them hard.

Here's a video about it for those who are interested:

https://www.youtube.com/watch?v=V2xnXArjPts&feature=emb_title

It's true that guitar isn't an "exact" instrument like a synthesizer, and there are these sorts of discrepancies you'll run into if you're very sensitive to pitch.

-Carl.