Okay, but you said he avoided it. You are free to not be satisfied with the explanation, but he did address it.
Also, he said not using a unique login name would cut costs and be less confusing. Let's be fair.
Oh yeah, like it's so confusing having a unique login name. Really, the only people this would be confusing for are morons, so I don't think that is a factor at all. No, this is about cutting costs, nothing more.