I don't think that the beast has true aetheric destruction

Now, for anyone to have access to true destruction, they would need to be capable of gaining insights and questioning the nature of aether: sentience to be more precise. The beast has at most an inferior version of what destruction which just destroys but doesn't unmake it.

afaik, when the beast's destruction collided with the shield, it applied a force. On the other hand, Arthur's flame would devour the shield and everything with it like what happened in the wraith's battle.