The reason for the "Click to view more data..." prompt is to avoid a situation when the embedded application "steals" the scroll ability from the main page. If the embedded dashboard is part of a larger page this should allow the user to have better scroll experience in the containing page.
When the time/map chart is present, the "Show all piecharts" link is often below the visible area thus it did not receive any special handling for the scroll.
However, now that we have the Embed Control API, one of the possibilities that it could enable is to automatically sync the height of the
iframe element with its contents, thus removing the need for this "click to view more data" link. If that would work for you, we will add it in one of the upcoming versions.