when having built rtc as a module the clock initscript might be run before the module has been loaded (and so waits without success for /dev/rtc). When the module is loaded via modules autoload everything works nicely, but when the module is loaded via coldplug it is not there when clock is run. I know that this is a quite exotic szenario, but if it causes no problems i don't see a reason not to change the order, it can make things work for more people without having to tweak their module autoload list.
add rtc to your modules.autoload if you insist on building it as a module
