Updated: Oct 23
One aspect of this mushroom is that it is incredibly absorbent, especially if not sealed correctly while dried. The reason we have to dry them is so that we slow down the conversion but also degradation and loss of actives, because water is where chemical reactions happen. The actives are sealed inside the top layer of the mushroom when dried and that helps keep it shelf stable if kept cracker dry. But if you powder it, you remove that protection. So, the reason why you would powder it is only when you're going to use it immediately to smoke.
Definitely don't use the powder to make oils (the oil will take far too long to get through a filter with powdered amanita), don't use it in capsules as it could be far too strong and make you sick but also you don't know how long they've been powdered in capsule form if you purchased them.
The only reason to powder them is if you know for certain how much of it dried you can ingest and you don't want to taste it and you know you will use up the powder within a few weeks. Otherwise, crush them up if you are going to smoke it and only crush up what you need in the coming week or this session.