So my question is, this lifting each finger max is an exercise thing only? Or should I really try to play like this most of the time while playing fast scales.
It is recommended by the exercise but it is not necessary for keyboard technique more generally.
Warning: extreme fence-sitting follows:
There are several famous pedagogical approaches to keyboard playing, and they are sometimes contradictory. In general these approaches originated from observation of famous virtuosi, so all the approaches can work.
Applying to your case, some players are trained with this maximum raising of the fingers, others are not, and both approaches can work.
In general, speed is aided by minimizing unnecessary work. Raising the fingers to strike from a greater height than needed is unnecessary work and takes longer.
Fast scales, which you asked about, do not need any significant raising of the fingers. They can be played very close to the keys.
On the other hand, if the scales must be both loud and fast, some technical approaches require raising the fingers more. Others derive the increased power from arm weight and forearm rotation. I would recommend reading more on those standard terms if you are interested. This answer would grow to unreasonable length and lose focus if I wrote about them here.
I have one item of specific advice if you practise a high finger action. Make sure that your finger plunges fully into the key, and that the strength is in the playing of the key, not before; physically, that maximum acceleration occurs during depression of the key. I have seen even quite advanced pupils with a high finger action who waste most of their downstroke in just reaching the key: their playing mechanism is "too high". By the time the key begins to depress, most of the energy has been wasted. The result is a superficial "skating" on the keys and anemic tone.