re: Does anyone actually believe this

As I touched on before, as well, is that Alexander's authors are all well-known throughout history. The New Testament, by and large is anonymous as I wrote earlier (when Stacked wasn't debating me).

The primary sources written by people who actually knew Alexander or who gathered information from men who served with Alexander, are all lost, apart from a few inscriptions and fragments.[1]

Contemporaries who wrote accounts of his life include Alexander's campaign historian Callisthenes; Alexander's generals Ptolemy and Nearchus; Aristobulus, a junior officer on the campaigns; and Onesicritus, Alexander's chief helmsman.[1]

Finally, there is the very influential account of Cleitarchus who, while not a direct witness of Alexander's expedition, used sources which had just been published.[1] His work was to be the backbone of that of Timagenes, who heavily influenced many historians whose work still survives. None of his works survived, but we do have later works based on these primary sources.[1]

As I said: It'd be damn near impossible to create a guy like Alexander the Great, and there's no motive to do so.