You buy into the myth and error that something open to intellectual discernment, nuance, application of experience, a call to  conscience, and rigorous study intrinsically CANNOT be prophetic.  

"Ambiguity" is not the opposite of or enemy of "prophetic." It can even be an ally. 

 Something does not have to be prescriptive and legalistic to be prophetic. 

Poetry can be prophetic...music can be prophetic...intimacy can be prophetic...art can be prophetic---demanding rigid and unambiguous canons, laws, guidelines, and prescriptions can degrade ,  demean, and dilute the truth inherent in them. 

The topic of AL is LOVE for heaven's sake---please don't seek to turn guidance on love and loving into a rule book. Trust the love-experienced laity to read what the Pope says and to seek thoughtful understanding of how it applies to them. The Pope doesn't need rule book referees or instant replay officials in the booth to rule on what he says to the Church--or on how he says it.