Generally they do strike and constrict. I've seen them eat f/t casually like that, but not often. And usually eating sideways is not a sign of an overly-intelligent ball python. But if he's switched homes and he's still eating, yeah, let him do it however he wants. They're weirdly picky, especially when they switch environments, so just keep doing what works for the next few months.

Are you warming up the zombie mice with a heat lamp or a hairdryer at all? Generally if you warm up the noses of the mice for a few minutes, that'll help activate the strike instinct. And even if he still doesn't strike, maybe that'll help him find the nose of the mouse first, so he has an easier time getting it down.