This actually happened. Speed was around 160kts and thrust suddenly started to gradually increase, as did the speed. The glide had just been captured and I attributed the increase in thrust to the selection of Flap 3 whilst still not fully in a 3 degree profile. When speed increased to about 170 kts, towards 180kts (S Speed), I knew something was wrong and instinctively disconnected A/P and A/T. Simultaneously my colleague noticed his mistake and reselected Flap 3. Throughout these few seconds, i'm pretty sure that Vapp bug was still visible (there was certainly no bug at S Speed), and VLS did not seem to increase, and my intention was to bring the speed back down to Vapp. My question is, had my colleague not noticed his mistake, and I manually brought the speed towards Vapp. whilst Flaps were retracting towards position 1, VLS should simultaneously increase, shouldn't it?