https://www.jwfacts.com/watchtower/mediator.php
The Watchtower Society uses an eisegesis approach to arrive at doctrine; that is, it creates a doctrine and then manipulates scriptures to support it. This requires resorting to rhetorical fallacy to convince people what they are saying is true.
A classic example of this is in a 1989 article explaining why Jesus is not mediator for all mankind. Following are some quotes;
"Is Jesus the Mediator only for spirit-anointed Christians or for all mankind, since 1 Timothy 2:5, 6 speaks of him as the "mediator" who "gave himself a corresponding ransom for all"?
The Bible contains both basic teachings and deep truths, which are solid food for study. ...
To grasp what Paul is saying, we must first appreciate that the Bible sets out two destinies for faithful humans: (1) perfect life on a restored earthly paradise and (2) life in heaven for Christ's "little flock," numbering 144,000.
... The Greek word me.si'tes ...
Clearly, then, the new covenant is not a loose arrangement open to all mankind. It is a carefully arranged legal provision involving God and anointed Christians.
This should help us to understand 1 Timothy 2:5, 6. Here the reference to "mediator" was made after the five other occurrences of the word in letters written earlier. Hence, Timothy would have understood Jesus' mediatorship to be His legal role connected with the new covenant. ...
Consequently, 1 Timothy 2:5, 6 is not using "mediator" in the broad sense common in many languages. It is not saying that Jesus is a mediator between God and all mankind. ... The apostle John referred to these at 1 John 2:2. But he indicated that others too will receive the benefit of Christ's sacrifice: "He is a propitiatory sacrifice for our sins, yet not for ours only but also for the whole world's."
Those of 'the whole world' are all who will gain eternal life in a restored earthly paradise. Millions of such approved servants of God now have that earthly hope...." Watchtower 1989 Aug 15 pp.30-31
The article starts saying this is solid food, indicating that if you don't agree with or understand the conclusion you are spiritually immature. It then shows that in order to understand the role of the Mediator another Watchtower doctrine must be believed. However no Scripture is given to back up the doctrine that humans will be resurrected onto earth, as there is no Scripture that makes such a statement. In fact, when Revelation 7 and 19 discusses the Great Crowd it places them in heaven "before" the throne. (See Paradise Earth and Great Crowd) The doctrine of the Mediator is built upon this shaky foundation.
There follows lengthy inclusion of Greek definitions. This seems to be a diversionary attempt to give an air of authority to the article, as the discussion has no bearing on the existence of a secondary class or answering the original question.
The article next attempts to add weight by inclusion of a commonly used Watchtower word - "clearly". This term is constantly used in Watchtower articles to reinforce a questionable point. The writer also claims to be privy to what "Timothy would have understood".
Not content with limiting the mediatorship to only 144,000 people, the article goes on to add that the propitiatory sacrifice, which the Bible says is for the "whole world's" sins, only applies to those that gain life in the earthly paradise. Since the Watchtower teaches billions will die at Armageddon without any hope of a resurrection, it is excluding all worldly people alive from the value of the sacrifice as well.