Imagine that you announced to the entire public that you were going to make 4 movies, but you realized after making the second one that you need 5 movies to explain the plot. The overall story has already been made, finalized, etc, but there's just not enough time in the remainder of the screen time to fit in 5 movies, so you are forced to choose what to keep and what to throw.
Anno thought, "Shit this sucks. But between two choices: PURE plot, and no Ikari Shinji (the one in the preview for 3.33) OR a HUGE GAPING FUCKING HOLE in the plot, and full Ikari Shinji and Kaworu (actual 3.33), then I'd choose the latter. The second one has more emotional impact, and why not make the last movie wrap up everything properly? Maybe we can even expect the audience to fill in some details of what happened in the 14 years."
That, or, "TROLOLOLOLOLOL. Bitches. TAKE THAT MINDFUCK MEDLEY. Revenge for the budget cuts in the first one. That's what you fuckers get. "
We'll never know.