Autism diagnosis does not really focus on social interactions. Difficulties in social interaction are a side effect but it is not how they diagnose the condition.
Can you cite a reference to a diagnostic tool for autism which doesn't "focus on social interactions"? The DSM-5 certainly seems to indicate that social interactions are important diagnostically (excerpt below):
"""Persistent deficits in social communication and social interaction across multiple contexts, as manifested by the following, currently or by history...
Deficits in social-emotional reciprocity...
Deficits in nonverbal communicative behaviors used for social interaction...
Deficits in developing, maintaining, and understanding relationships...
"""
DSM-5 criteria for ASD have as criterion A "Persistent deficits in social communication and social interaction across multiple contexts". So if one doesn't have persistent deficits in social interaction, one doesn't meet the criteria for ASD. So this is a core part of the diagnosis of the condition, it is a mandatory requirement for diagnosis.
I have gone through the autism diagnosis process myself, it is very flexible so as long as you have the stereotypical problems with social situations they will give you a diagnosis if you want it. I didn't want it so they didn't give me a diagnosis. I guess if there were parents involved who wanted something to blame they would have pushed for the diagnosis though.
https://www.autismspeaks.org/autism-diagnosis-criteria-dsm-5
"""Persistent deficits in social communication and social interaction across multiple contexts, as manifested by the following, currently or by history...
Deficits in social-emotional reciprocity...
Deficits in nonverbal communicative behaviors used for social interaction...
Deficits in developing, maintaining, and understanding relationships... """