Honestly, that's a pretty good take. Considering that welding/brazing would be incredibly hard (or impossible) with the tools available in antiquity, we're left with casting that beast in one shot. The thin walls and nubblins on all sides that need to permit molten bronze to fill, makes for a difficult to construct and pour mold. Heck, just constructing the master from clay or wood is non-trivial, and then there's the finish work on the rough casting.

So yeah, a practically useless paperweight that demonstrates how amazing your brozneworks is? Totally plausible.

Edit: Upon closer inspection, it might have been mostly turned on a lathe out of a chunk of cast bronze, with a ton of manual finish work. So, still very hard. The nubblins don't 100% interfere with the faces if you can get your tool in behind them, cutting from the axis of rotation, outward. Each face on the duodecahedron has an opposing face, making turning between centers easy. The nublins are also all opposed from each other, on the same axis, which would make those possible to also form on a lathe. It's the hollow inside that would require turning to remove bulk mateiral, then a pile of manual finishing work.