S. Madman

A 4.0L M278!!

Right.... https://carnewschina.com/2017/01/19/...se-car-market/

http://www.baicgroup.com.cn/news/2027?back_url=%2Fnews

I got a feeling that they are lying about the displacement to avoid higher taxes.

arsupisemnet

Not necessary. Historically the number used to correspond to atmospheric equivalent of engine volume, i.e. 500 - 5 liters, 600 - 6 liters, and so on. With the turbos it is different story. You could have 3 liter turbo engine with power of 4.5 liter non-turbo engine (like GL450 post 2014).
Plus each different country model has different ECU tuning due to local regulations. So GL450 in US goes as GL500 in Europe