Actually, while I share your skepticism about the argument, this isn't a very good counter—plenty of commanders in that situation would have been perfectly content to keep the young pliable boy on the throne. Each one of them would have had more power in that situation than they would in a succession crisis.

Indeed, in the event it worked out quite well for them. First conquer the world with the united Macedonian army, then partition the world between them when Alexander dies.