I personally find the DM agents recently more accommodating with award SDCs than in the past. Previously they were happy to standby. Nowadays I find the agents just push it through (when I've just changed a simple nonstop to nonstop). This weekend, I wanted to SDC from an award flight only selling Y online to one a few hours later with 100 seats open. System asked agent to collect 15,500 extra miles; she proactively said that's silly given the booking situation and had it even exchanged. Maybe I have been lucky recently...also sometimes apparently the system errors out with award SDCs and when that happens agents are allowed to just process as even exchange.