Oh, this is the argument Dr. Grande (that's the surname, right?) used in his video and it has been parroted since then.

She has DID. She lives it every day, and she trusts the professionals who provided information on DID because they have practical knowledge of it.

Also, DID is no longer controversial in the sense of "is it real?" Today there are people who disagree as to how it should be treated etc. Those who deny its existence aren't taken seriously, so why would anyone bother with it?

Also, this approach to science only matters when it comes to DID, curiously enough. Is Dr. Grande skeptical of depression, OCD and so on? Is he advocating for the medical field to try to disprove their existence and condemning those who don't?