I don't think this is the right distinction. Osama bin Laden for example was killed in person by American special forces, which probably isn't that unusual a type of targeted killing but rarely makes it into the news, and the method didn't seem to attract much mainstream comment.

I think we're looking at more of a tribal distinction, or possibly a cultural feeling that different rules apply in engagements among states than between states and non-state actors. (Compare the death of Chris Dorner, the shooter targeting LAPD officers a few months ago.)