Both - as they're commonly referred to - "Poland A" and "Poland B" comprise of significant portions of the population. I can't see why life in one should be considered "real", while in the other, not. There are two sides to this picture.
Because capitals are show off places in oppressive countries. The reality is outside. I grew up in a small city in USSR and sometimes speak to people that grew up in Moscow or Leningrad. The difference is huge... They often owned cars, had frequent access to bananas and oranges, and the stores were generally adequately stocked. Not for us and the rest of the country..
That's true, but my parent commenter referred to the entire North West (which is, generally speaking, more well off in Poland) not being "real". Not just Warsaw. Ciechanów or Piła, both rather small towns, could hardly be considered show off places.
Overall the gap was more along the lines of big cities vs. province as you say; rather than geographical. In a centrally planned economy large urban centers were overprivileged in the pecking order.