This is a BowJunky video that shows the apertures of top compound archers while shooting during competition. Whether you coach compound or recurve primarily, this is well worth watching.
Even top flight compound people show aperture movement while aiming. Do realize that compound bows are easier to hold steady than recurve bows due to their greater mass. [ More mass means more inertia, which equates to harder to move.” The simplest example is how much harder it is to move a boulder than a pebble. They are both made of rock and their size is not an issue … their mass is the issue.] Conclusion: recurve apertures move, too … probably more so than compound apertures.
You are steady when the movement is minimal, not when it stops. What “minimal” is must be learned … and improved upon if possible.