SmartThings commands get sent to the cloud and operate on a “set & forget” principle. IOW, they don’t necessarily execute in the order sent. I believe you need to rethink your Routine configuration. For example, you could have your Routine disarm SHM based on presence, and then add a separate smartapp that triggers upon the state change of SHM to send a command to open the garage door. I believe the Trigger Happy app will do what you want.