Only because Miller doing it to Rondo would cause Rondo to fly about a mile and it would look worse than it really was, just as Rondo doing it to Miller made it look not as bad as it really was.
The refs have to make the call in real time. A flagrant with seconds left in an OT is a disgrace.
There's an old saying. "All's fair in love, war, and the last 10 seconds of an NBA game."