Sorry to say that, as person with DID, I totally disagree with you on this point. How can you say that alters doesn't exist at once? How can you be so sure that alters doesn't have relations between one another?
For sure you don't have DID, this is clear! No offense intended, simply the will of not allowing others to speak about something that I live with since 50 years.
I truly get that is very difficult to grasp what is like living in more than one inside the same body/mind, so I please you to consider to learn directly from DID people the way it goes. You might appreciate, as professional, having a look to the DID community on Reddit, one of the very few places where we can be truly understood and I hope a place where you can find better understanding of the reality we live.