It was always intended to get people to Heathrow Navpi, that’s a huge part of the selling point. It takes pressure of the Piccadilly Line for commuters as well. It was very much designed and sold as a feeder for Heathrow but it won’t be as “luxurious” the Heathrow Express, as expensive or as pretentious.
The way everyone is shouted at to wait on the platform while the “SECURITY CHECK” is performed is just a joke.