No, they are different things. I am honestly quite confused as to how you could think that they were the same thing. They both exist as a constellation of separate diagnostic criteria, for example, and the internal phenomenology of both is different. You can have one, but not the other, or you could have both.
For example, here's a quora where someone with both talks about it: https://www.quora.com/What-is-the-difference-between-ADHD-an...
Or if you prefer a more 'scientific' source, here's one examining the comorbidity of ADHD and certain disorders, among which Schizoid Personality Disorder is one: https://www.elsevier.es/en-revista-revista-psiquiatria-salud...
They find a correlation, yes, but they are certainly not one and the same.