Defensive driving has its place. In similar situations where either a) someone's coming rapidly to an intersection and looks like he/she won't be stopping, or b) a cyclist is coming where in my experience in that area many barely stop or don't stop. I can only assume the LEO was thinking along these lines.
Of course, LE frequently is listening to dispatches and finds opportune times to sit and eval for a few moments. Might occur if already stopped at a traffic sign.
And too, in some parts of the country, particularly in some communities, it's commonplace for the other to be given the right of way, even if technically the "book" says the one has it.
Myself, I just go with it. I tend to drive or ride exceptionally defensively, assuming the other at a cross-street is likely to do the worst possible thing just as I'm at the most-vulnerable spot. So, for me at least, it's no skin off my nose to get positive confirmation from the other if there's any question. I tend to be in no rush. Though, if clearly there well in advance, and there's no question of the other person taking liberties, I'll continue on and take that right of way the way the other assumes I will.