Ah…
We considered this when designing the tool. But seeing as how images come in all sizes, the safest thing was to sample the single pixel so that if someone put a small image in there they would not be grabbing colors from all over. We are open to adding more functionality to this in the future if you want it. Perhaps an expanded user interface so that you can set the width of the sample point? Or I like your idea about using the zoom as a trigger for which sampling happens.
Keep in mind that in many cases, the image itself is down-sampled when it is brought into the worksheet. You might find that some areas in an image are “averaged” because of that. See the Opening Images section of the manual for more information.
Also go ahead and send in a Feature Request. In ColorThink, it’s under Web > Feature Request. Tell us why you want this, and what you will use it for, and we will definitely consider developing it for a future release.