Apparently the companies making coffee for planes have (de)pressure chambers to conduct tastings.

If that is true, they they are running incredible margins to afford that. A human sized negative pressure chamber is not any easy thing to obtain or maintain, even to airplane climates specs. Most likely, they rent out time on someone else's chamber or just take a chartered flight and test on the plane.

Not true, I took an Aeropress on an international flight and made fresh coffee throughout the flight. It tasted great. The hot stewardesses had no problem letting me use their hot water which was nice.

You're actually arguing that the environment of a plane doesn't have any effect on people's sense of taste because one time you totally liked your cup of coffee on a plane?