Actually, there should be no assumption at all where we don't know the explanation. Nothing is lost by waiting while the answers are gleaned,and a naturalistic explanation is the likely outcome anyway.
Ironically, "naturalistic explanations" are, at their core, a punt, since the question, "What caused or causes nature?" is unanswered. And unanswerable... by science.
A naturalistic explanation for nature would be a tautology.
Since I don't personally know of one good solid documented supernatural event, you'll excuse me if I assume until one comes along that whatever may be lacking in the explanation for a thing, it's probably not a violation of the laws of physics.