Why does it matter?
The beginning of the gentile times is not based on the destruction of Jerusalem. Only the WTS tradition is. Because the WTS is hard headed, they want to stick with Russell's reasoning (though they changed everything else). And everyone against the WTS goes against that.
The gentile times is based on when the promise to David got paused. Jehvoah told David that he seed That is not about the destruction of Jerusalem but when the kings in the line of David lost their sovereignty. Since they lost that before the destruction of Jerusalem, then it does not matter when Jerusalem was destroyed.
2 Sam 7:12 "I shall certainly raise up your seed after you, which will come out of your inward parts; and I shall indeed firmly establish his kingdom. 13 He is the one that will build a house for my name, and I shall certainly establish the throne of his kingdom firmly to time indefinite. 14 I myself shall become his father, and he himself will become my son. When he does wrong, I will also reprove him with the rod of men and with the strokes of the sons of Adam. 15 As for my loving-kindness, it will not depart from him the way I removed it from Saul, whom I removed on account of you. 16 And your house and your kingdom will certainly be steadfast to time indefinite before you; your very throne will become one firmly established to time indefinite.”’”
That is for David, then Solomon then on to be kings in Jerusalem on down to Jesus. Well, Jesus never became king. So what happened. The Gentile times.
"your very throne will become one firmly established ". Prior to Jerusalem's destruction the throne was lost when they were invaded and were subject to other nations and that started the gentile times when then ended in 1914.