I think they put some numbers there and have not tested anything.
The game is still bugged and not optimized: it's far from perfect and I think that airplane's performances are the last things to worry about for now.
1) complete the interfaces
2) optimize the graphical engine
3) optimize the physical engine
4) check the airplane performance
...
...
...
19) Add new maps
20) Add new planes
If it was to me I would have hired more experienced persons to develop a good engine, both graphical and physical: only at that moment I would have started to create 3D models... instead we have super detailed models who can't appear on the map.
PS: AI cheats

. Don't use it to compare performance. Fly with a teammate.