Well... first, the articles you are referring to are 5.5 years old...and was not written by the MS SharePoint team. Best Practices, to my knowledge are published by the manufacturer to support designed services/features.
My point is that by deploying multiple CA's, you could potentially run into a scenario where multiple admins are applying changes to the same services at the same time...sending the farm into an unknown state..
I am not stating that 1 CA instance is best practice, I am just saying that I have spoken with a few Masters who have brought up that fact.
Sorry for the contention