The downside of this practice, at least for others, is that it ties up award ticket inventory unnecessarily. Someone else might miss the opportunity to book a lower mileage itinerary (that the shotgun ticket reserver ultimately might not use) and be forced to pay more miles for the desired itinerary. Then, later, the person holding the reservation cancels the ticket when redemption rates are higher. Question: are we even sure that a cancelled award ticket puts a seat back into award inventory or could it possibly go into revenue ticket inventory instead?

Getting away from the particulars of the OP's situation, this does prompt memories of folks coming here to ask about potentially shady practices. Sometimes in the context of "The airline has disadvantaged me, so I am justified in doing this", not recognizing that what they intend to do risks disadvantaging other customers. Too often, such posts have have focused on not whether it is the right thing to do but, rather, "How likely am I to get caught?" The latter communicates the self-realization that the intent is not the right thing to do. "Deep down, I know it's wrong, but I am searching for validation."

Today's dictionary word is solipsism.