The scope of the labelhas definitely expanded. But the article here isn't saying that 'people who need to veg out have autistic burnout'. Instead its saying 'people who were already labeled autistic seem to respond in this peculiar cluster of begaviors when stressed in burn-out like ways'.

If the article is correct, and the behaviors are quite unique to people labeled autistic, it actually supports autism as a diagnosis rather than just a label. Labels with predictive power regarding psychological behavior have some semblance of a diagnosis.