Seems like accurate information to me. If he is a co-writer and a co producer as you claim, then he wrote and produced the movie. If people assume he was the sole producer and writer, well thats their bad assumptions, not a dishonest practice or even remotely approaching a "vast difference".
Did Spielberg Direct Indiana Jones?! Well yes he did, but there were several other directors who did lil action scenes and "B-crew" stuff as well, does that mean Steven Spielberg needs to advertise every "B-crew" director whenever he talks about the movies he produced or directed?