Just a bystander here, but if USBC had reversed it's decision then they are in essence saying "sorry for all the commotion, but we were wrong before; but now we're right."
Then, in the future, when could we believe that they actually have a clue? Do we believe them when they make other such judgments? Or do we wait for the second time they test to believe them?
USBC had no choice but to stick with their decision or they look like amateurs.
Personally, that minor difference in the core would be no advantage in the hands of 99% of bowlers, however, USBC has their spec limits and they must be adhered to by all companies, or why have them in the first place? How far out of spec is immaterial. The limits are the limit...
If one were used against me in league I still would not care (personally) because the difference, at least in my mind, is very small.
Anyone who was holding their breath and hoping for a reversal has a better chance of a visit from the "real Easter Bunny".