I explain :
First, press sustain pedal down, then play a key, then release the key, then release sustain pedal, then wait the sound to competely die (300-400ms), then press sustain pedal down again. We can still here the convolution resonance even though the note stopped sounding.
Actually, it happens during all the time the convolution has not ended.
It can result in some very bad sounding chords' chains using sustain pedal.