@Frederic Ward yes, provided you are repeating the DESIRED motion. And that's the trick of it, because the actual path to improvement on guitar is not directly to the final perfected motion, but rather a gradual refinement of the motions. The big error that occurs IMO is that an assumption is made that the slow motion is in fact the same motion as the faster motion, but done more slowly. That's the problem. It's NOT the same. It's actually a somewhat different muscle memory. Players become frustrated because they are hammering away at the slow motions thinking that is what's needed to speed up, when in fact, they are reinforcing the wrong motions.

@Frederic Ward yes, the trick to THAT (avoiding the boredom that sets in with repetition) is about learning to shift focus to listening, improvising variants, and moving the mechanics up and down the neck to not only be doing the same mechanic repeatedly, but by such a method you can simultaneously also learn the fretboard in its entirety!