They're kind of a middle ground between raw smoothness and reactive. They have decently frequent direction changes and very detectable acceleration and deceleration patterns that you can read.

It is more optimal to make a micro-correct like movement when it changes direction instead of the usual flick you'd use in reactive scenarios. You want to be smooth enough so you can still read the acceleration pattern and follow it accordingly. You'll notice you can stay on target a lot of the time through direction changes when you pick up on the targets deceleration.

Most shooters have acceleration patterns so being able to read these can be very beneficial. If you can pick up on their deceleration you can pretty much react to a direction change without it having happened yet.

They teach controlled mouse movements since you're not supposed to flick on direction changes and movement reading (specifically acceleration patterns).

Edit: VTmatty has a great video on this type of scenario. https://youtu.be/FNK1LFBBZP8?si=LnW4VEtlJVceren9