In 1971, they made a clear distinction between the Governing Body and other legal entities. From w01 1/15 p. 29:
At that unforgettable annual meeting in 1971, a distinction was clearly drawn between the spirit-anointed members of the Governing Body and the directors of the Pennsylvania corporation. Still, members of the Governing Body continued to serve as directors and officers of the Society. Today, however, the question arises: Is there any Scriptural reason why the directors of the Watch Tower Bible and Tract Society of Pennsylvania must be members of the Governing Body?
The answer is no. The Pennsylvania corporation is not the only legal entity used by Jehovah’s Witnesses. There are others. One is the Watchtower Bible and Tract Society of New York, Incorporated. It facilitates our work in the United States. Jehovah’s blessing has clearly been upon that corporation, though its directors and officers have been mainly of the “other sheep.” The International Bible Students Association is used in Britain. Other legal entities are used to promote Kingdom interests in other lands. All of them harmoniously assist and have a role to play in getting the good news preached earth wide. No matter where they are located or who serve as directors or officers, these entities are theocratically guided and used by the Governing Body. Hence, such entities have assigned tasks to perform in furthering Kingdom interests.
And from w90 1/15 p. 26:
In modern times the Governing Body has been closely identified with the editorial staff of the Watch Tower Society and its board of directors. But the Governing Body differs from that legal corporation, as the speaker pointed out: “Since the corporation’s existence is purely legal, with a fixed geographic headquarters, it can be dissolved by Caesar, the State.” Not so the Governing Body, which is not a legal instrument but the members of which “are appointed through the holy spirit under the direction of Jehovah and Christ.” Thus, the Governing Body continues to function and to receive the unqualified support of Jehovah’s Witnesses worldwide.