The Watchtower has never disputed that the Greek text of Wescott and Hort doesn’t include the divine name. (Except the shortened form Jah, in Revelation) In fact they have stated this fact a number of times when discussing the topic.
Their argument is that the original NT used the divine name, and on that basis they restore it. How much clearer could they be? On this issue a number of NT scholars agree with them, that the divine name occurred in the original NT.
My point about Yaho is that there is evidence that this is how first century Jews called their God, and therefore it would not have been unusual for Jesus to have done so.
It’s like asking if President Lincoln or President Nixon used the word television, or TV. Even without direct evidence it seems reasonably likely that Nixon used this common word and that Lincoln couldn’t have used it, for obvious reasons.
Since Yaho was a common designation for the Jewish God in the first century it is on the face of it reasonable to suppose that Jesus and his contemporaries used the name. The later NT manuscripts that don’t include the divine name date from a period when the divine name had been removed from the LXX also, so are not good evidence for use in the NT period itself.