But in the trailer is seems like Gohan's charging into a fight
How many occasions did Gohan go SSJ ?
I explained it earlier, I've read up on the full movie as well as watched some scenes straight from the movie and he only goes SSJ when giving power to Goku.
He used is ultimate form when he charged at bills.
The one you posted earlier was simply a mistake from 1 of the earlier trailers that was released.
So while it was a REAL trailer, it was a mistake most likely by the animation team.