I've been told those "cyclist dismount" signs have no legal basis behind them and so can be ignored - maybe someone can clarify.I would tend to agree.
In particular a throttle seems to make for a more stable getway from stationary, you can keep both feet on the ground as you pull away.
Thumb throttles, I am not so sure about, I have knocked one of those a few times when you get off to push the cycle just before one of those 'Cyclists must dismount' signs.
And a full throttle, easy to forget about it, you lean bike against wall and off it goes.
Half throttles seem the safest to me.
Anyway, I prefer a thumb throttle as your hand soon gets tired with a twist throttle.
I don't think a thumb throttle is any worse than a pedal getting knocked and activating the PAS. Yes you can turn down the PAS sensitivity, but then it doesn't activate soon enough when you need it!