Yes but it's very clear that any time Mark is shirtless/naked in the movie he's hurt or starving or something else that is Not Good and it does have this interesting thing where not even the audience gets the benefit of seeing Matt Damon all sexy etc etc, because there's no one else up there on Mars, /not even the audience/
exactly, almost none of the nudity (even the partial) is fan service-y in any way - except for maybe the bit somewhere around the water making scene. it’s not included for the audiences benefit, its always necessary and there’s a plot point tied to it every time.
even the aforementioned bit, which was just him taking off his shirt, could have been a way of visually explaining mark’s decreasing ‘modesty’ as time went on - kind of telling why the hell he got out of the shower naked and waked around, when at the start he was in a robe.