According to the manuals you do need more than normal memory issues to be DID. If you never lose time, you can only have a partial diagnosis, strictly speaking. But also some people lose time without realizing I hear, so I guess it might happen. One of my friends switched, but it was just for 20 minutes so he could easily deny ever switching because he is sure he doesn't do that.

Also another friend who does not lose time got changed from DDNOS to DID and I have no idea how it even happened, because he does not lose time. He has very extreme alter states but they always remember each other.

So.. short answer, heck knows...