Good old Boeing...
Dani,
Already B-767/757 autothrottles have Alpha mode, which will not allow speed to go lower, if limit Angle of Attack is reached. This implies that TOGA thrust will be given, if that is what it takes to prevent further speed decay.
Just off the top of my head, difference between AI and B setup may be in the fact whether A/T has to be engaged or not, for this protection to work.
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More or less the same goes for A/P modes - they will also respect speed limits, but do so when engaged. In B, if pilot manually puts the a/c on it's nose or back, the flight controls won't stop him. In A (FBW) a/c, the pilot is prevented, also in manual flight, from performing outlandish deeds by the flight control system.
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This TOGA lock thing gives me another argument to illustrate the difference between moving and non-moving thrust levers.
To get out of TOGA lock in the A-320, you have to disengage A/T.
If you just pull back the thrust levers, nothing will happen. You would notice that nothing would happen, for instance, by looking at the engine instruments. Then you would have to consciously reason why the engine indications have not reduced to idle and then you would realize - oh, got to disconnect A/T.
In moving thrust lever setup, you may also have to disengage A/T to cancel ALPHA mode, but if you just pull levers to idle without disconnecting, the engines will go to idle and your hand will feel the A/T working against your hand, trying to move the levers forward again. In this way, you get what you want immediately, not only after the observation, reasoning, action cycle has been completed, and, the road towards realizing what you have forgotten may be more direct - from the hand that feels opposition directly to realization, without a knowledge based reasoning process.
EMIT.