@slowwalker, You better explained where spread Mahayanist Buddhism and Hinayana Buddhism. Yep...Hinayana Buddhism deeply spread in Sri Lanka. Those stone lotus basin Stood in Beopjoo-sa temple amazing architecture used from old citizens. Also it's really rare design.

nobody seemed to curious why they built that stone sculpture in this temple.

But you have best opinion why they built those Stone Lotus Basin Stood. Thanks for great pics and better explanation.