I left PEK on the 19th, it became quite bumpy right after take off, the F/As had to stay seated for quite sometime. It remained rock and roll until almost the end of meal service, then the seatbelt sign was finally off for the 1st time. Of course what people did next was to line up for the lavs. The flight was smooth till landing though.
Maybe the wind was a factor to your friend's case?