What cons does a high guard have?

You don't really understand how vision works. You're correct in that rods are for ambient vision and cones are for focal vision but the ratio of rods to cones is 20-1 or around abouts. Cones don't give any indication about how something is moving in relation to yourself, that is solely up to the ambient vision even if something is directly in front of your eyes. Nobody is 'Cone' dominant. If somebody could possibly be cone dominant then they wouldn't be able to judge distance and timing at all.

 

You are creating a strawman of absolutes. Everyone has cones everyone had rods. Some people have more rods than normal. Some people have more cones than normal. For example as a general rule women will have a higher ratio of rods than men and men will have more cones. That is one of the main reason why some people have superior focused vision and others have better night vision and peripheral vision. Someone with a high amount of cones isn't blind nor is someone with a amount of rods night blind.

And I never said that cones are sensitive to movement rods are.