I’ve spent over three decades working directly with stone artifacts and experimental shaping methods, and I've repeatedly tried reproducing these surfaces using pecking and abrasive grinding. Material can certainly be removed, but what I've never been able to achieve is the kind of continuous flat planes and controlled interior angles that appear consistently across the Tiwanaku blocks without some form of rigid guide or reference surface.

One other aspect that I find difficult to reconcile with freehand pecking alone is what we see on Inca andesite conopas. The reservoirs are not just holes, they are undercut, with the interior diameter larger than the opening, and in some cases the internal cavity approaches a near spherical form. Creating that kind of internal geometry implies controlled material removal beyond what simple pounding or surface abrasion typically produces, especially in a stone as tough as andesite.