The extra fitting, instead of just slipping on the hose, is an extra leak point. Also there is no need for a shut off valve. If you ever need to "shut off" the tank outlet you can pinch the hose with vice grips. That valve is also an additional leak path. You can just install a barb fitting into the outlet.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn