Well put Gareth. I agree.
I would question the DVSA view that a handbrake will help if rear ended.
In a rear end the rear tends to lift, thereby reducing the effectiveness of the handbrake, but it is locked on.
Applying the footbrake applies braking to all wheels, whereas the handbrake is just two.
Additionally, the front brakes are more important in stopping a car, than the rear. However.
I also confess, when driving manuals, I sit with the footbrake applied; even on hill starts. Not in gear, and not riding the clutch.
On a hill start I engage the handbrake momentarily, keeping the button depressed so as not to lock it, only when about to move off.
Despite all these bad habits, some years ago I passed my Driving Examiners test.