No, what they were probably thinking was "We can breathe, we can save suit air and we're going to decontaminate in the ship later anyway" so they did it...and thus saved us from five extra minutes of dialogue about airborne pathogens, "parts per million" and atmospheric testing devices.
Lol - did you SEE their decontamination procedure? Given the choice of roasting or having a time-limited visit on my first day, I think I'd keep my helmet on until after we'd tested our impetuous volunteer.
Plus later dialogue suggested that they didn't screen them after they came back. Rapace suggested they run bloodwork only after one of them started showing symptoms. It's a bit late to quarantine at that stage.
Given how inane some of the dialogue was, I think I'd have been more than happy to cut some of drivel out and add in a bit of common sense science.