You're missing the point. He didn't choose to go down pit entry and then leave it again to gain an advantage (What Kimi did). He would have been better off if he didn't start to go down pit entry. The entire sequence of events left him, at best, in the same position he was in before. It was against the rules, so he got a reprimand to warn him that it isn't acceptable. But given the circumstances where it was provoked by someone over the radio shouting "In! Out! In!", he didn't have even whole seconds to decide what to do. Now he's been given the reprimand I would expect a stronger penalty if he does the same thing again.