"Both methods fraught with danger to those below."
Have you ever done this? We are not talking a mounted spare which would be interesting. Unfortunately I've had to do it several times and letting it hit close to flat on the ground is the best way.
"Have you ever done this?" Not from 15' up in the air with truck tyres.
"as you just roll it off with someone to stop it "
Do you really use this method. Surely not. Even weirder would be if you found someone silly enough to be the back-stop on the ground.
As I said, very dangerous even with an unmounted tyre, particularly the roll-off method. A 22" tyre weighs more than a few pounds (60, 100???) and is large and has a lot of momentum and is made of elastic material and will bounce unpredictably and it wouldn't be very easy to try and stop it.
The other consideration would be that in trying to make sure it did land nice and flat, you probably stand a very good chance of following it over the side one day and that would be painful.