Kifis,
I suspect you have misread the arguments put forward.
In the height over speed debate, the point at which height is preferable to speed is once Vx, Vy, Vxse or Vyse (as appropriate) has been attained - and not before.
If I'm correct in my interpretation of your post then, yes I agree with you, as long as the speed is lower than Vx, Vy, Vxse or Vyse. But once that IAS is reached any further increase in speed reduces the efficiency of the conversion of fuel into performance.