I think perhaps in places like China, where everyone is essentially expected to understand Mandarin to some degree (although to what degree and the ability to speak is a different matter) that this is somewhat less of an issue. Of course there may be the odd person here an there without the ability to understand Mandarin, but with the education system based in Mandarin, I would expect the occurrence of such passengers being extremely low.

I recently caught an Air Canada flight (LAX-YVR) with my French speaking mother.As expected, there were announcements in both English and French (the FAs were both French speaking) but my mother could barely understand the French announcement due to the thick accent and difference in vocabulary and even some grammar!

I put this down to both my mother and the FAs speaking different non-Metroplitan French