The interior rooms were never physical...the society said in a 98 WT that they denote the inner room of each congregation...then they added if there is anything else to this prophecy then it will be revealed at a later date.
They have never said it is KH...in fact they have said the opposite in that it is not a physical location.
I quote an old public talk I used to give:
Can I read you a quote from August 15th 1998 Watchtower page 19 paragraph 14. This was quoted at our recent district convention.
In the near future, the greatest time of tribulation ever to strike the human race will break forth suddenly. (Matthew 24:21) When it does, servants of God will need as never before to display confidence in Jehovah’s righteousness and in the direction provided by his organization. In a symbolic way, they will then confidently obey God’s injunction: “Go, my people, enter into your interior rooms, and shut your doors behind you. Hide yourself for but a moment until the denunciation passes over.” (Isaiah 26:20) Already they have entered into the protective atmosphere of over 85,000 congregations in 232 lands. Whatever may additionally be included in the injunction “enter into your interior rooms,” we can be confident that Jehovah will help us to carry it out.