During RedHat 7.2 shutdown the scripts save mixer settings to /etc/.aumixrc, whatis correct. But during startup the system does not use /etc/.aumixrc to initialize the mizer. Previous versions of RedHat did not have such problem.
It's done whenever the module is loaded on demand, through post-install commands in /etc/modules.conf. Loading modules in rc.sysinit isn't really the right place unless it's necessary (to lock down ISA buffers, for example).