On BA at least there is a mechanism that eliminates the middle seat by spreading the armrests into it, making the aisle and window seats a bit wider. But seat pitch is the same as the rest of the plane and it's barely less cramped. However I was impressed that they served a hot meal on the short flight LHR-AMS.

Nearly all narrow-body service within Europe has a similar setup. On KLM they don't have the middle-seat crusher and you pay extra for the same seat with better food and drink up front vs. the back. The cabin divider if there is one is on a track and can be moved to magically make business class bigger or smaller, but the actual difference is largely imaginary.