/bin/true sets the return code to 0, signifying success to the modprobe process, /bin/false sets it to 1, signifying failue, and producing said message. Due to

/bin/true sets the return code to 0, signifying success to the modprobe process, /bin/false sets it to 1, signifying failue, and producing said message. Due to the way modprobe may be hooked by various things, its best to use /bin/true to ensure less breakage.