It literally doesn’t matter if bi and pan are the same thing because even if they somehow were, it’s okay for two words to mean the same thing. That and we haven’t scientifically proven that there isn’t a need for the word pan, if you catch my meaning.
And even if that need doesn’t exist they STILL mean two different things.
So really, cut it out with the “pansexual is unnecessary because nonbinary isn’t real and therefore it means the exact same thing as bisexual” bullshit.