The capture actor’s position isn’t arbitrary, and you can have several, with overlapping volumes, and they will blend with each-other, the main thought from the documentation is to have one large actor, for gross reflections, and have little ones for things like glass windows, and other objects that reflect light to a high degree.
Furthermore, the capture actor (silver ball) is the location the reflection is rendered, so you could have an actor that changes position, or one that’s more in line from where the reflection has to be perfect.