I wouldn't say it's multiple personality disorder in the clinical sense.

1. The 'disorder' itself isn't causing them any emotional problems, keeping them from succeeding in life, impairing relationships with others, and so on. They seem happy and functional. That's the caveat most psychologists attach to a definition of any mental illness along with the symptoms. It's part of why, for instance, homosexuality was eventually removed from the DSM--it's not the 'disorder' causing the depression and suicidal urges, it's people in society being homophobes.

2. The symptoms don't quite match up. The personalities apparently share memories, they're pretty self-aware about the matter and there's some measure of control over who is 'out' at any given time. Also they don't mention any kind of sexual abuse or other intense childhood trauma that would have led to the disorder.

So I really wouldn't compare the two conditions.