It can be other things. Some of why I didn't get stuff done when younger was actually a symptom of PTSD from unrelated trauma. Basically my stress response is messed up and so anything I could link to stress or shame can make me avoidant, which snowballs into not doing the thing and more stress.
When I unlinked daily tasks from shame and stress I could suddenly do them, as I actually have ok executive functioning when PTSD isn't messing with me to cause avoidance which as I understand would not really be the case for ADHD. Although PTSD and the like can also pop up in ADHD people who were bullied for their symptoms.
You know how you end up with socks that don't have a mate?