A footnote makes a further distinction. If the speaker’s own explicit explanation, rather than preponderant juristic opinion, identifies a meaning of a mushtarak, the expression is treated as mufassar. That explanation removes the particular uncertainty remaining under a merely inferential preference.
Preponderant juristic preference: muʾawwal; applicable with a possibility of error.
Speaker’s clarifying statement: mufassar in this case; the text describes its legal effect as certain.