Alexander can't have taken Tyre in September of 331, because he fought at Gaugamela in October of that year, unless his army had jets in their asses. Even then, Alexander assaulted Gaza after taking Tyre and proceeding on to Egypt. Whoever is saying that Alexander visited Siwa before taking Tyre and Gaza is simply mistaken, the entire reason why Gaza had to be invested in the first place is that Batis was preventing Alexander from marching down the coast into Egypt. The final assault on Tyre took place, according to Green's dating, on July 28, 332, and the siege of Gaza took place between September and October of the same year. Alexander stayed in Egypt from late October of 332 to around April of 331. He was proclaimed Pharaoh on November 14, 332, and probably reached Siwa in February of 331

ah i figured a missing piece of the puzzle.

clearly, the evidence suggests that Alexander went to Siwah AFTER his siege and conquest of Tyre,

but after that he had been in Siwah, he then RETURNED again to Tyre, a couple months later, before from there then launching out into his final conquering of the Persian Empire.