It’s most likely a protective transport/storage cap rather than a normal light-shaping reflector.

That matches the shape and behavior you described: it mounts to the Bowens front, protects the COB LED area during packing, and the opening may simply allow some ventilation or reflect a shared cap design used on other Godox lights. If the light overheats with it installed, that’s a strong sign it is not intended for normal operation.

One community answer suggested it might act like a snoot, which is a modifier that narrows the beam by blocking spill. But if it causes overheating, you should treat it as a cover, not a shooting accessory.

So in practical terms: use the standard reflector or other Bowens modifiers when the light is on, and use this piece only to protect the front of the light during storage or transport.