I do think that smothering is more typical. The only reason I discount that here, is his claim that Shanann strangled the kids. If he had smothered them, I think he would have said that’s what he saw Shanann do. It just doesn’t make a great deal of sense to lie here.
On the flip side of that, maybe he would have thought (wrongly) that the claim that she smothered them, would have made his postoffense actions appear worse.
He may have thought that smothering would have meant that the kids being saved by a call to 911 was more viable, and in turn, his actions would appear more aggegious.
The autopsy will likely tell us, but I’m leaning towards strangulation.