freitasm:I don't know why the surprise. Installed a door opener to a shed in in-law's place. Yes, there's a cord you can pull to disable it but the cord is from inside. If there's a power cut then there's no way to pull the roller door up since you can't disable it from outside and no other access to the shed.
You can have an external lock barrel connected to the release cord. Unlock, pull barrel out of door until release trips.
The manual release can be a security risk. It can be possible to fish for the pull cord with a length of wire shoved over the door.