So, what you are saying Doc, is that it if I dig deep enough, I may find evidence to suggest that at some point the Romans may have been short of timber and that it may have been on one of these occasions that Jesus was put to death. There is absolutely no doubt in my mind that at some point, they may even have run out of nails! Perhaps. Who knows? And all of this so that at some point in the future the Watchtower organisation would have a little tit-bit that they could point to in order to justify their views.
I put it to you that the Watchtower abandoned recognition of the cross as the means of execution of their saviour because they wanted to distinguish themselves from mainstream Christianity. I would also suggest that the same is true of birthdays, blood transfusions and toasting, along with a multitude of other teachings. There is no logic behind these teachings. They serve only as an attempt to distinguish the Witnesses from other denominations, which of course in fact they don't because most of the Adventist breakaway religions believe in much the same thing because they all stem from a common source.
That is not meant as an affront because I'm guessing that you already know all this stuff anyway. After all, it's no great mystery!