Jetpack Sharing Pinterest Button – Weird Behavior

When configuring the sharing buttons, the Pinterest button exhibits different behavior depending on which Button Style is chosen. When the “Icon only” option is chosen, the Pinterest behaves like a Pinterest button should, with the browser window giving the visitor all the options of photos on the page to pin. When, however the “Official buttons” option is chosen, clicking the Pinterest button triggers a pop-up that only features one image option. Why?

Many thanks in advance.