This whole concept is an exercise in cognitive dissonance. First the Watchtower splits the baby under Rutherford. Rutherford realizes that the number of Witnesses world wide is exceeding Russell's 144,000. Rutherford realizes that a new carrot has to be fashioned. What do we get? The Great Crowd of Other Sheep!
However, now that the Watchtower is on the hook for the New Covenant only applying to 144,000 going to heaven. So Jesus sacrifice seems to be reduced in benefit. The waters get a little more murky.
This is a great example of how all Abrahamic religions (Judeo-Christian-Islamic) are not "truth" or at least eternal truth that is of value. Truth is this context is like an IP address. It comes in two formats - static and dynamic.
For Abrahamic religions truth is dynamic. The goal posts keep getting moved. What was good enough for salvation from God's wrath one day is no longer good the next and so on. When the goal posts get moved, those in charge double down on the change and decry "heretic!" to anyone who disagrees.