Yes, VAST is specifically not ADHD, although a disorder is really defined by how it affects you. For example, some people worry too much, other people have generalized anxiety disorder, and the effect it has on your life is what separates normal from disordered.
"The person finds it difficult to control the worry.... The anxiety, worry, or physical symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning." DSM-IV/V
Some of the strategies used to help people with ADHD are used to help with VAST-related loss of focus and procrastination, but medication is probably not recommended for those diagnosed as not having ADHD but likely having VAST.
It's funny, I googled VAST and the AI search insisting that it's the same as ADHD, it's just a reframing of it
It sounds similar but almost coming at it from the opposite angle. ADHD is when your brain's baseline is not producing or using dopamine properly. VAST almost sounds like a sort of burnout, where your brain is overwhelmed and cannot process stuff anymore. The symptoms are the same, the effects are the same, but the cause is different.
ADHD root cause is internal lack of stimulation, VAST root cause is external overwhelming stimulation. That's how I understand things anyways