during the whole action he does not stand still for a second
Pretty sure it’s just a “stand in the rain” interaction like a lot of people love to do when it’s raining (including myself lol).
Also, “stand still” in English doesn’t always mean not to move your body or limbs at all. It can mean to simply “stay put” (stay in one spot and not walk anywhere else). However, limiting your movements is implied in some situations.
Does the Zoi walk around or stay in one spot as they feel the rain? Regardless, saying “stand in the rain” would make more since.