Chimbu, if there is no thrust there is no acceleration. There is no requirement for acceleration to reduce gradually. Movement is subject to inertia and momentum but acceleration is not. Any perceived delay in deceleration would be due to delays in the engine responding to power lever inputs.
404Titan, with your speed trend you are seeing delays in engine response, the engine will not go from T/O thrust to idle instantly. The statement that acceleration stops the instant the thrust levers are closed is wrong because the engine can't respond that quickly, but if you think that you can remove all thrust and still experience positive acceleration then you are also wrong.