I think they're talking about current captains and F/Os who've completed their 2 years on a base or their freighter commitment and wish to move or return to Hkg. Apparently some of them have been told that there's no vacancy in Hkg so they have to stay on a base.
As the update says, the right to return to Hkg has always been a cornerstone of our employment. It's also fairly clearly written in the basings agreement that after 2 years an officer can voluntarily elect to return to Hkg (para 15.1) and has been common custom and practice since 1993 when basings were first introduced.