That’s interesting. It’s the inverse of the problem I typically see which is that pyglet and retina displays don’t always get along. See thread linked below.
My guess is that it’s still basically an issue of it correcting for something in both cases when it only needs to on the Mac, and so everything is getting bigger and distorted on windows. That said, I can’t figure out why it would be doing it that way rather than working on windows and failing on Mac! It may have to do with the monitor you’re using, are the settings for it comparable across the two?