What the Linux kernel sees is a user granted all capabilities that happens to be userid 0 that is root. Little error here. Linux kernel does not know that userid 0 is root. Its the password file that gives userid 0 the root name. If you want to you can change the default number for the default user in the Linux kernel to something other than 0. Yes it would confuse some applications badly. Nothing kernel side demards user 0 be all powerful.
