No matter what seatguru said, it is for sure UA is economy plus. Seatguru is just plain wrong and giving the wrong impression to other people never flown UA.

The reason UA is calling as economy plus, because it is basically economy plus a few more inches of legroom, nothing else.

All airlines when they call premium economy, other than more legroom, it is also about more seat width usually 1 or 2 seats less per row depends on the plane, some also have better amenities and better meals. But then these airlines would charge a premium (often close to discount business) for premium economy seat, where UA only charge $100 tops for long haul flight.