In John 6 Jesus said to partake is essential to get everlasting life
Prologos, that is another topic. I am not saying that it is not related but I am only focusing TD commentary on the great crowd.
It is twisting the scriptures to say the great crowd survives , or exists as an entity before the great tribulation.
I understand what you are saying but what the wt concludes seems logical when they reason that in order to come out of the gt or survive they must exist as a gc beforehand. The wt I quoted from above admits they were wrong about the gc prior to 1935.