Everything in existence is a physical phenomenon. That doesn't mean physicists have authority on everything.
You might as well consider every philosopher an authority on everything because every problem ever solved was solved by thinking and that's what philosophers do. While in reality philosophers are only authorities on (the history of?) philosophy.
that's too harsh. philsophers are experts at a particular way of thinking: logic. it is surprisingly powerful for clarifying ideas and advancing knowledge, in much the same way as mathematics or the scientific method are. we would not say mathematicians are only experts on "numbers"
Logic is actually part of math. There are even few different logics math worked out.
Some philosophers follow logic but apply it to unanswerable questions. Some can't even do the logic part rigorously enough. Personally I have no respect for this field of culture and humans that pursue it. All of them are not even wrong.
You might as well consider every philosopher an authority on everything because every problem ever solved was solved by thinking and that's what philosophers do. While in reality philosophers are only authorities on (the history of?) philosophy.