I didn't realize how poorly typed my post was... I'll have to edit that!
To answer your question, the percentage of total charge decreases as the size of the charge increases. For example, a .1 grain error is 1% of a 10 grain charge, but only .1% of a 100 grain charge.
While decreasing the charge error to zero would be of some benefit, the reduction in ES would only be a small portion of the total. There are simply too many variables to deal with in order to get a statistically valid zero ES. I have found other ways to limit ES in my loads. Would reducing my load error from +or- .05 grains to +or- .01 grains improve my ES? Of course it would! In my chosen game (F-class TR), would it make a difference in scores? Maybe, once in 20 matches it might pick me up one point or 1 X. In the big scheme of things, I have much bigger fish to fry (my skills could use a lot more work).
By comparison, Jay's F-Open rifles could very well have been costing him 1 point and/or 1 X on a much more frequent basis with the ES and SD problems he was experiencing. Both of which could be the difference between winning and being in 10th place in his discipline. F-open tends to be a bit more perfection oriented than F/TR score-wise.
Off to fix my horrible grammar and spelling...