this is due to clamping system, which remains robust although any plastic.
But, you might say, a big softbox to a cobra flash is perhaps a little excessive.
Probably, but
firstly, my softbox is not monstrous and any studio flash supports it without flinching
On the other hand, a Godox Ad360 has the power of a small studio flash, and the flashes cobra, if one is a little tight, we can put several door with multiple claws (in Godox also sells one that supports 4 flash units specially designed for this support)