This is a terrible headline for an already over-editoralised paper. The entire study revolves around 2 people (twins) and thus no statistics can be performed. Statistics is careful to prune away hypothesises but I am happy to state that this paper is wrong based on its lack of care and shitty title. The description suggests ABA therapy + diet. ABA therapy does in fact improve the percieved symptoms of autism, but it…
You have statistics even if 2 people. The probability of the result matters, if you have n=1 and cure cancer it would be incredibly stupid of you to claim it proves nothing.
In this case ABA treatment is already well known, and there is significant experimental research into it's efficacy. It's demonstrably not effective in 'curing' austism in most people and has measured, known 'side effects' including anxiety, depression, or other mental health problems.