Why do some people say to use 0.007 mm (approximate pixel size) for the CoC on a Canon 5DM2?

The 5DM2 pixel size is approximate 0.00645mm in size and so some people talk about using 0.007mm as the CoC. I think canon said once they use 0.035mm for DOF charts, full frame normal is 0.033mm, Zeiss has the formula of dividing the sensor diagonal size by 1730 which gives 0.025mm, and some people say they use 0.02mm when they are going to a large print.

I understand how magnification and viewing distance effect the CoC, but I’ve never seen any concrete formulas about how it’s done assuming normal eyesight. So why would one advise using the approximate pixel size (0.007mm) for the CoC on a 5DM2? Is this for a specific magnification/viewing distance combinations, and if so how would you go about figuring those out?

Using 0.007mm for the CoC is mentioned here: http://www.dpreview.com/forums/thread/2844882#forum-post-35942031 http://photography-on-the.net/forum/showthread.php?t=1166799

In the second link it’s mentioned that a 5DM2 8″x10″ print is an 8.5x magnification and viewing pixels at 100% on a computer screen is 45x magnification, is the 45x number accurate? How would did they come up with that?