Even without the overlap, the wt generation theory is wrong. The first century generation did not pass away before the destruction of Jerusalem; but wt says that the anointed generation will pass away before the destruction at Armageddon.
Trouble is, if you say otherwise, question this teaching, it is not just a theory, but truth cast in stone, you will be disfellowshipped.
what does it really mean? It means using the Frederick Franz example, Armageddon would not come until ~ 2075.