The attacks happened 4 hours ago. We would have already determined if there are any injuries to US personnel. BDAs take longer. Strategically, however, if the goal is to deescalate, then you don't come out of the gate crowing about zero casualties and saying the damage was so minor your BDA only took an hour to complete.
Our troops are not potentially dead. There's zero doubt we've been formulating very aggressive and tight protocols to quickly do casualty and damage assessments and get the data back to DoD. They've probably been refining and practicing since the Soleimani strike. Plus, we have very good radar in the area. For whatever reason (whether strategic or symbolic), Iran chose to hit a base about as far away from their own territory back home as they can in Iraq. That gave plenty of time for our personnel to shelter.
I'm telling you, the military, especially in this type of situation, doesn't take hours to report casualties. It isn't ongoing combat. It was a fairly quick event. You fully know I'm not at all a Trump fan, but he's obviously been made aware we have no casualties. DoD would've known definitively about any casualties within an hour or so. I think they intentionally slow-walked the release of casualty info to give themselves more time to formulate a response (and to have more potential options) and to make the Iranian strike look more significant than it was. It's a DoD driven strategy I guarantee you.