Doubt in visualizing filter concept

In this lecture sir told that we have to maximise the dot product of x and w.
so w is already trained so we cannot change w.
so x has to be equal to w/||w||.
So we have put a constraint that x should be a unit vector.
So is this because it will simplify the soln or in reality the x is unit vector.
Because even when we do feature scaling that does not mean that x is a unit vector right?

Can please anyone clear this doubt? @Mitesh_Khapra @Prem @GokulNC