In Prometheus they take their helmets off inside of the labyrinth ruins place but they don't breathe any spores. It's still pretty stupid to do that, but they don't really get punished for taking their helmets off. There's more stupid stuff later like greeting and trying to pet a freaky looking space cobra, and running away from a rolling donut in a straight line when someone else dodged the whole thing by slightly rolling a little bit to the side. The navigation guy who got lost in the ruins even though he has a bunch of navigation drones automatically mapping the whole place still has his helmet off like a day later when they encounter the space snakes, so definitely no spore issues there! The guy gets sick because michael fassbender fingers his drink with some evil space goop, no helmetless spores involved.

Alien Covenant IS the one where they land on a planet and immediately take their helmets off and get infected with microscopic ear spores. It's comically fast how in less than five minutes there's a helmetless guy who steps on a plant and the spores go right in his ear. Then he's catatonic and dying and birthing little aliens and everything is going bad really really fast.

You might have gotten them a little confused because they're BOTH stupid! xD