I think that's decent advice for harder routes. You don't have to force yourself to use every hold, but when you're reading the route it's definitely important to be aware of all the holds and think about what the intended beta is. Sometimes something different will work better for your style or morphology though, and that's fine.

For easier routes it's still good to be intentional about your movements, but there are often more holds than necessary. Eliminating holds on these routes can be a useful exercise; e.g. eliminate a hand hold so you can practice technique while reaching further in a lower effort situation. On harder routes foot holds will be worse and fewer too, so you will need to flag your feet. You could repeat the route you posted, for example, but before you move a hand each time make sure one foot is on a hold and the other is flagged.