The rear end of the flamethrower looks like the one from the film, the front and nozzle is WTF?
I woulda thought 'Ripley's flamethrower' referred to the flamer and pulse rifle taped together. The pulse rifle is on the outside for a right hander. I suspect (hope) that thing in the trailer isn't meant to be an accurate depiction of "Ripley's flamethrower", and is just another weapon and down to the trailer edit.
Though all this talk of flamethrowers, makes me wish for a playable Parker with a Nostromo flamethrower.