opting out of bulk emails also opts you out of SMS messages
Now, if you opt out of bulk email messages, you won't receive any SMS messages either.
The field name is is_opt_out (which seems pretty general) but the user interface clearly says: "NO BULK EMAILS (User Opt Out)" And the description re-enforces the notion that this is a user-set variable for not receiving email messages.
Most people use mass email and SMS in very different ways, especially given the limitations on the number of SMS messages can be sent (which makes them more targeted).
As a result, it's reasonable for someone to opt out of bulk email but expect to get SMS messages.
My preference would be to eliminate this check so that SMS messages ignore this field. My second choice would be to change the language in the UI.