If that embedded reporter was aware the unit he is embedded in intends to target civilians then absolutely. If he doesn’t, goes along and takes pictures and then celebrates it with them then he’s complicit in that war crime.
As it so happens, this is almost exactly what the NYT contracted freelancer did. The question here is if NYT should have done any further due diligence and refused to purchase the photos. I don’t think there’s a moral quandary in this specific case.
I agree there is a moral difference between the two scenarios you proposed, but based on current OFAC guidelines, they are more likely than not the same. But that’s only for US persons. Most countries impose greater constraints on speech and the press and international outfits like AP and Reuters may need to worry about additional jurisdictions asking questions about their usage of freelancers with questionable ethics.