I don't understand the limit on bullet weights? I'd use my 223 at matches if I could use 80.5 Fullbores.
I can sorta see it as they're limiting ammo to something like what you can buy in the store that will run through a magazine.
Whenever you have equipment rules that are anything other than "anything goes" (like USPSA Open division), someone somewhere is going to be pissed that their pet peeve isn't accommodated.
As long as everyone is held to the same rules, doesn't matter.