It's still on the spectrum. Loneliness shouldn't be treated by detachment and doing so can only lead to a lack of interest in social relationships, a solitary lifestyle and an exclusively internal fantasy world.
You can call it what you want but it's definitely Cluster A.
I'm no expert, of course, I'm just a guy speaking out of line on the internet, but... From what I saw from a cursory Cluster A search, this behavior is literally not even tangentially related to the criteria for Cluster A disorders. It's not paranoid, it's not schizoid, it's not schizotypal. These are lonely people who disassociate a part of their internal monologue. Please elaborate exactly, in your opinion, which Cluster A criteria these people display.
How is it not schizoid? It's literally treating loneliness by directing attention toward one's inner life and away from the external world. I'm no Eugen Bleuler, but his definition is exactly this, the self in exile.
If you want to talk about specific criteria, from the ICD-10, I fear it in the long term would lead to:
1. Almost always choosing solitary activities.
2. An excessive preoccupation with fantasy and introspection.
3. Neither the desire nor existence of any close friends or confiding relationships (or only one).
You're extrapolating. Those aspects aren't part of the matter. There's nothing about these people that indicates they want to be alone. Making a tulpa literally depends on the person's desire for companionship, not their desire to be alone.
Schizoids are lonely and they choose (quite paradoxically) to be alone because of it. The internal fantasy of the schizoid exists solely to fill the hole left by their lack of emotionally intimate relationships.
That is, the steps of the schizoid personality is:
1. Loneliness
2. Escapism in the form of internal fantasy
3. Choosing to be alone, because the internal fantasy is judged to be enough
You can call it what you want but it's definitely Cluster A.