I would say this is more of a Facebook limitation.
You can still export your Gmail contacts... just not to automatically to Facebook (unless Facebook starts allowing easy export of its own data... which is the bigger problem right now, IMO).
When google said in the past that users are free to take their data and leave, I dont remember any caveats being in place. Whether they leave to join a idyllic commune or a kleptocratic dictatorship imo their data should freely go with them.
You can still export your Gmail contacts... just not to automatically to Facebook (unless Facebook starts allowing easy export of its own data... which is the bigger problem right now, IMO).