One nasty thing about overlapping ASD and ADHD is that one masks the other, to an extent. ASD puts you in a rut, with repetitive behaviors, but ADHD moves you out of it to seek new shiny things. ADHD makes it hard for you to focus, but every now and then ASD kicks in and you compensate that lack of focus by being hyper productive and doing in a 18 h binge (or 38 h once for me) what would have taken most people 2 weeks.
The usual questionnaires sometimes fail to identify either, especially in adults with regular masking going on plus the masking the two disorders give each other.
I think the science is catching up to it, I don't know whether there is an established differential diagnosis protocol yet. And after one is made, there is the hurdle of establishing it as praxis in the medical profession and health programs / insurance.