What you are describing in paragraph 2 is not specific to autistic people, although it is common. Introverts in particular can also become drained from social activity. There is some overlap.

Masking also is not necessarily the source (or sole source) of social exhaustion and instead the exhaustion may come due to greater sensory sensitivity and/or cognitive processing requirements, which are common in autism. Furthermore; masking has other purposes such as avoiding bullying, social exclusion, and other forms of negative outcomes; the intent and effort varies by the thing being masked and the person.

YMMV; it's a spectrum.