You have to remember, as a soldier you are never going to know what's happening except in your little area. If people around you are doing badly, you're going to run to save your skin. People see you running and they run and soon everyone is fleeing. Battle over.
Muslim generals liked to set up on hills to direct battles, but in the age of hand-to-hand combat and slow communication battles will still usually end relatively quickly and with one side panicking first and the other running up casualty numbers in the pursuit.
But skilled or at least charismatic leaders were be able to stop some flow of panick, and to redirect charges.
It's why the Battle of Guadalete lasted, so its said, 2 days. If you have someone with less important numbers but having the right position, he would have a far less active strategy at first.
Banners, or even trumpet-like were often used for communication and were kind of designated targets. Arabo-Muslims from the Umayyad era had a lot of banners in battle for, partially, this reason.
As XanXar wanted to devellop a vassalic based tactic for armies, it's both an advantage and an issue.
It would force a "decentralized" command, where a leader seeing the battle isn't going to its best interests, could decide to flee the battle simply and purely and let its suzerain deal with it.
BUT, this decentralized command allow more reactive units and quick tactics decision on precise points.