It is not hoarding. It is stockpiling. Hoarding is something that technically cannot be done until AFTER something is rationed.
Like when people were preparing beforehand for Y2K by stockpiling food and water. It isn’t hoarding. Preparedness is never hoarding. Trying to buy all the stuff up AFTER a disaster or something like that, THAT is hoarding.
And there are other factors at work. The demand for, and price of metals increasing is one. Trying to purchase at the current cost, expecting it to go higher later. People purchasing a valuable commodity for the future is another.
The normal price/demand relationship causes quantity demand for a good to fall when prices rise. Sometimes this relationship gets inverted, such that rising prices trigger increasing demand. This occurs in speculative bubbles, and in hoarding situations. Whether or not you want to call the present behavior "hoarding", it clearly represents an inversion of the price/demand curve.