Our range won't allow holster practice for this reason. Someone needs to design a holster where the side opens upon withdrawal and requires to user to close the flap after re-insertion.
The U.S. military HAD ‘flap holsters’. They were great for ‘protecting’ the firearm, but lousy when you had to pull the gun from the holster, in a hurry.
Sad to say, but I do think that gun guru Clint Smith said it best. If your gun is not on the target, keep your booger finger off the trigger!!