I think they are witnesses of Jehovah because of witnessing regarding the events of 1914 which the first century christians were not witnessing about.
the book The Nations Shall Know That I am Jehovah-How? (WTB&TS 1971) pages 19-22 talks of the exodus fron Eygpt and says on page 22
'Now the responsibility was upon those liberated Israelites to serve as witnesses to their descendants' and goes on to quote Isaiah 43:1-12
In the Insight on the Scriptures (1988) Under the heading Israel and subheading Birth of the Nation it says
'God now saw fit, however, to deal with them, not strictly as a patriarchal society, but as the nation of Israel, which he created and to which he gave a theocratic government founded on the Law covenant as a constitution'
So I assume it was at this time of the exodus that they became a nation.
In the Watchtower of March 1 1925 there was I believe an article regarding Revelation 12 and the Birth of the Nation, God's Messianic Kingdom in 1914. and i believed as Jehovah's Witnesses we were fulfilling the scripture in Matthew 24:14. which i related to the good news of the birth of the Kingdom in 1914. Something that the first century Christians were not witnesses of but were witnesses of Jesus. (1Cor. 15:3-8) The birth of the Kingdom was surely caused by Jehovah.
That's my view.