Thanks Wikipedia.
"A press conference is a media event in which newsmakers invite journalists to hear them speak and, most often, ask questions."
Journalists are not invited to ask questions at any of the E3 conferences. Nothing here says it must be live. I fail to see how Microsoft inviting journalists to hear them speak from a stage is a "conference" while Nintendo inviting the same journalists to hear them speak from a pre-recorded video is not.
In fact, right there it says it's a media event. Video is a form of media. Nintendo's E3 conference is even called a digital event. It's a press conference, held during E3, largely about E3 (such and such will be available to play on the show floor). So in every regard, this should be considered an E3 conference.
