Considering I've never had a "salt and pepper is not a seasoning debate", I can't answer that question. I've debated that something that is advertised as "seasoned" such as "seasoned fries", or "seasoned salt", is seasoned with more than just salt and pepper... or that if you google "steak seasoning", you don't just find companies selling a mixture of salt and pepper. I can't help if others want to play stupid semantics games to try and move the goal posts in an effort to prove they aren't wrong. You're a good poster, I have no desire to start a heated discussion over what is clearly a misunderstanding.
Back to the topic, I've never had a whoopie pie that had marshmallow fluff, it's always been cake icing. Since I'm talking about my experience, it's not debatable. I've had my fair share of them in my life too, so the point is that it's not universal (or even necessarily common at all) for whoopie pies to use marshmallow filling.
You should probably try some homemade ones and not the fake over the counter Gobs.