nothing odd or unusual, this is the uk exams policy - the school reports usual way of working to the exam board. Diagnosis, psychiatrists report etc, all totally irrelevant.
Two children could have identical ADHD, and one has a diagnosis, and a Psychiatrist report, and one doesn't, they both get treated exactly the same by the exam board, who refer ONLY to the usual way of working ,reported by the school
This is particularly important in the case of a child with ADHD with a parent who also has ADHD, as the child may well suffer significant disadvantages, with parents more likely to be unemployed, in prison, divorced, etc and much less able to provide a diagnosis and psychiatrists report.
Therefore, the worse ADHD is in a family, the less likely a child is to have "paperwork" related to their ADHD, so in education, and in exams, it is very important that children without the paperwork are given the same support as children with it