I would be nice to have some more context on the company. I like to think this respect to detail is representative of how their service is run, but I don't know what the service is.
I think it has to do with how to get perfect pixel in illustrator. If you just draw a line even if you have your rulers set to pixel you will get anti-aliasing once you render it in for instance photoshop. So what you do is that you offset it in points as far as I can remember by .5pt that way PS will render it nicely.
Having said that I still don't know why someone thought of this to be HN worthy it's a rather old problem with a rather old solution.
This is one of the great examples of the difference between a graphic designer that charges $200 per hour and your friend's cousin who can do the entire project for $20.
See, I am, and I'm still not getting what the story is here especially in relation to "pixel perfect." The guides demonstrate an attention to detail in getting a good corner, but that's nothing to do with the final pixel rendering as such.. really just good Illustrator path building.