That’s my bad for conflating the two. Indeed they are not the same in ICT-11 but! diagnostics is moving towards the direction of treating them the same. ADHD and ASD have extremely high comorbidity and it has been proposed many times to classify them together because the symptoms overlap (difficulties at school, aggressive behaviour or temper, lack of social skills, etc). In fact it has become so difficult to find distinctive features of ADHD both in diagnostics AND treatment (both are usually treated with cognitive behavioural therapy and in more severe cases medication) that it has been proposed numerous times to drop their distinction in the ICT, but this hasn’t happened yet. Good paper to the point:
I don't think that's the conclusion of the paper you linked, although there are papers suggesting that ADHD and autism are essentially subtypes of a single overarching disorder.
The more common view is that because prevalence of attentional deficit in autism is so high, it's rare to find someone with autism who isn't also able to fit an ADHD diagnosis. This might mean a shared common ancestor as it were, or perhaps autism has attentional deficit as an intrinsic part of the disorder rather than people with autism also often having ADHD.
The other direction is the amount of people who have ADHD who also have autism. In this case, while the overlap is higher than the general population, it is easy to find people with ADHD who do not meet the diagnostic criteria for autism.
Put more simply, people with ADHD aren't necessarily autistic, but people with autism are usually ADHD.
CBT is not a first line treatment for ADHD in Australia. Indeed standard CBT is contra-indicated because it requires the kind of "homework" that ADHDers struggle with. There are CBT variants tailored for ADHD however.