It might help you to think of the thrust and pitch separately.
1)with low thrust, you let speed decay to Vprot. Then aircraft pitches down to maintain Vprot. Then you pull stick back and it allows you to go to V.a.max, but no lower. You release the stick again and it pitches down to accelerate to and maintain Vprot.
2) At some stage between Vprot and V.a.max, you get A.floor. This only does one thing. Orders TOGA from the engines which remains until you remove the thrust lock by pushing the instinctive disconnect. The position of the levers has no effect on the thrust at this stage. Even if you move them up and down, the thrust from the engines is locked at TOGA. This is not an autothrust function and there is no speed mode.