i could be wrong but it seems quite different to me.
I understood that our preaching work of the good news was necessary for our salvation as we support those commissioned to do this specific work. ( Ezekiel 24:24, Romans 10, Matt 24:14, Matt 25:45)
Watchtower June 1 1968 page 331
On the Joyful March to Mankind’s
Millennium
Arguing
against a literal future millennial fule by Christ, some have claimed that such
a teaching would chill the missionary ardour of Christians to make disciples of
all nations. (Matt. 28:19,20) But not so! Today no people are more zealous in
carrying out this missionary commission than are the Christian witnesses of
Jehovah, who believe that the 1,000-year reign of Christ is literal and future.
In comparatively few years these have grown to more than a million. Today they
are carrying out this commission in 197 lands and islands of the sea and that in
169 languages. Last year they devoted 184 million hours to this work!
And no
wonder. What good news they have to tell the people! They proclaim the good
news that the millennial rule of Christ will begin with this generation and
that it will mean ever so many blessings for the people :..
As I believe this was part of the good news, gospel that we preached it needed to be true. I don't think that what was thought about John was part of the good news that was preached or something that was believed your life depended on preaching. That's my view.