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).