Why are the relics of Vulkan that He'stan wears not Primarch sized? And why are they worn and not stored securely?

Apologies if this is a silly question, but I was under the impression that the three relics Vulkan He'Stan wears were made by the primarch for the primarch, which would obviously make them oversized for a normal sized Astartes.

But the model of He'Stan, and the art he's featured in seem to have all those artifacts (Spear, Flame gauntlet, and cloak) be perfectly fit for a normal sized Astartes.

Did I miss something? I can see if Vulkan the primarch specifically made these items for an Astartes, but again, I was led to believe these relics were made by him, for him.

Why are the Salamanders okay with the Forgefather going into battle with these precious relics? From reading the Nick Kyme books, it seems that the forgefather often operates almost independently. Sure he can call on assets of the Chapter and it's successors, but generally he seems to be pretty solo.

So with that said, isn't the risk of losing him and the relics he wears kind of an unnecessary one, no? Because if He'Stan falls. They've now lost three mega important relics.

Thanks for the responses, cheers!