I am not an Asian. And I can't say FAs tell me goodbye systematically.
But you know what is almost systematic? When I say hellonin Chinese to a Chinese FA, especially on a Chinese airline, 99% of the time they answer in English.
Because, you know, we not Asian cannot possibly speak Chinese.
Sorry but this laowai does. Often better than their own English. And English ain't my primary language anyway.
Systematically I have to explain to them, I am taking the time to address myself in your language because, yes, I KNOW Chinese.
So, I guess I am coming from an angle similar to yours. People judge on the color of your skin. But this is definitely not limited to whites, Westerners, etc.
Now, surprinsingly, when I speak Japanese - which I do a lot less than Chinese - FAs answer to me in Japanese about 50% of the time. Not sure what this is all about.