If the Text Message tab on automated messages is left BLANK, then it won’t send out an SMS ever. So if you don't want a specific automated message to EVER go out via text message (like the request review for instance), then you need to leave this section blank. See screenshot below.
If the SMS tab has some copy in it, then it will send out via SMS if the default is to “Text” or “Email & Text” or if the email isn’t on file and the system has no choice but to send it out via SMS (even if the Default to is set to Email).