Yes Standing allows you to move and keep the spacing you need to put shots on him/her also it allows you to move and keep the gun away. The spacing also gives you time and room to fix any grip issues that might have occurred during drawing or clear any malfunctions. Also, most people are more hesitant to charge a gun pointed at them from a distance outside their reach. Creating space and drawing often times causes the attacker to stop in and of itself. Where as, when a gun is drawn from within reach, most times the attacker will instantly focus on it and try to take it away. Drawing while grappling does not give much room for error....and when a gun is introduced into the fight, errors are deadly for you. That's part of what they do. They analyze what has happened in fights combined with trends (with the rise of mma more people learning to grapple) then go to the mats and work on what tactics and philosophies that give best results. Figure out best practices then provide training to the officers in those best practices. Nothing is absolute....just trying to figure out what tactics and philosophy gives you the best chance of survival.