Millon's subtypes of schizoid don't at all resemble ADHD. Millon's subtypes are:
* aloof
* lethargic
* barren (intellectually)
* flat
* complacent or lifeless
None of these reflect ADHD, which is a dysregulation disorder resulting in the inability to form socially expected task-reward feedback loops. This means forgetting to do small chores once they leave one's sight even under the strong desire to do those chores, having strong emotional responses, needing higher levels of stimulation, and strong sense of impulse. None of ADHD has anything to do with whether or not one is displaying apathy or lack of interest in engagement broadly.
SPD is not a disorder of obsession. You might be thinking of the related-but-very-different Schizotypal, whose strange beliefs, sensory disruptions, and emotional impropriety I can see as potentially looking like ADHD.
You said it: Socially expected. They're failing to complete the loop because they're schizoid and social rewards aren't inherently motivating.
How do ADHD people act when their attention breaks? It's in the same ways Millon described. If you look at a schizoid person you can say that's the person and they have a masked state. Or you can see them as an ADHD person that has a checked-out state. But you're describing the same condition and the same person.
The ADHD approach is to medicate the patient so they can maintain the masked state for more of their waking hours. And avoid that terrible checked-out state! Except that's their real, schizoid personality. It's just less socially acceptable than the mask.
I didn't say it was a disorder of obsession. That's just their only tool for doing focused work if they don't have pills. If anything they struggle with maintaining obsessions. I'm familiar with schizotypal PD too and not accidentally talking about something else.
No, I don't think you understand ADHD. ADHD people do not behave in the way you describe when their attention "breaks". Their attention doesn't "break". Their attention is simply not regulated and so they will fail to perform tasks, which is not the same as having uninterest in those tasks which characterizes schizoid personality disorder. What you're describing as a checked out state is actually a reaction to frustration and distress that the ADHD person experiences as a result of being unable to regulate their attention long enough to perform tasks they want to do, which is not schizoid personality disorder characterized by not having a desire to form relationships and integrate with society. They're essentially completely unrelated conditions.
This also doesn't explain sensitivity to rejection or impulsive behavior typical of ADHD.
Again, ADHD is the mask state, it's not SPD. It appears opposite of SPD in order to mask it.
The frustration and distress are both there in SPD too.
Schizoids are indifferent to praise or criticism. Do you see how that's the opposite of sensitivity to rejection? Do you see how the schizoid's listlessness is the opposite of ADHD's impulsiveness? The mask is a compensatory state, like the narcissist's super-confident persona.
* aloof
* lethargic
* barren (intellectually)
* flat
* complacent or lifeless
None of these reflect ADHD, which is a dysregulation disorder resulting in the inability to form socially expected task-reward feedback loops. This means forgetting to do small chores once they leave one's sight even under the strong desire to do those chores, having strong emotional responses, needing higher levels of stimulation, and strong sense of impulse. None of ADHD has anything to do with whether or not one is displaying apathy or lack of interest in engagement broadly.
SPD is not a disorder of obsession. You might be thinking of the related-but-very-different Schizotypal, whose strange beliefs, sensory disruptions, and emotional impropriety I can see as potentially looking like ADHD.