Power is there to maintain a speed no matter what the configuration. As has been said the atmosphere is not a static entity. It is changing and so therefore will the power setting necessary to maintain the speed. Due to short lived shear factors the power could be quite variable for a few seconds. It is not uncommon to give a significant burst followed almost immediately by a reduction to datum; or equally a handful reduction and then back to datum.
It would be sod's law that this happens at landing gate and you have an overly keen PM with the SOP call of "continue" or "Go-around" and they close the latter.