I like the theory that it's an examination piece to qualify as a master metalworker. Casting a flawless dodecahedron could have been a way to demonstrate your skill. The shape is somewhat arbitrary: anything that's both difficult to cast and easy to examine for quality would work, but once people started making dodecahedrons that's what people expected and it became a kind of standard.
That wouldn’t really explain why the holes have different sizes on different sides, and why some of the dodecahedrons were found in wealthy women’s graves.
I don't have an opinion of the overall hypothesis.