I'd have to go back and look, but I've viewed it as a fallback argument for Michael if the "Terri's wishes" argument had failed.
There is no fallback if patient's wishes are not found. That is a necessary prerequisite, for now.
Florida Chapter 765 taken as a whole is, IMO, internally inconsistent; but by choosing through the clauses in a suitable path, the statutes will read as authorizing the outcome of the case.