I would think it depends on what the error was. IF the command wasn't necessary in your specific environment, then it may not make a difference.
The need for mkinitrd is to package up a mini-root filesystem with all necessary drivers (and commands) needed to mount the real root filesystem.
The advantage this has is that you can use the same kernel (and initrd) on vastly different hardware platforms without having to rebuild a kernel. You MIGHT need to rebuild an initrd if the driver you happen to need isn't there (I did this to add the virtio subsystem to use enhanced virtual disk drivers for use in a VM). No need to rebuild the kernel... or even any drivers - just add them to the initrd.
The memory for the mini-root (initrd) filesystem is released after the real root (on disk) is mounted via a "pivot root" command used in the initrd followed by a umount.