You do not have to move the vehicle, simply getting in and getting out does it. But that is still a bug. It should not be required to access the gear menu of the vehicle.

UP VOTING means that this is an important issue that needs to be addressed.
Please read the forums to understand the concept of the UP/DOWN vote.

http://forums.bistudio.com/showthread.php?147680-Arma-3-Feedback-Tracker-how-to-use

I agree, I was able to alt-tab out any number of times today to perform other tasks on my system.