Your global levels affect everything, if they are down as a result of Parkinsons disease or Lewy Body dementia, they are down everywhere. And a loss of 40% of dopamine neurons from baseline is going to affect mood. There isn't a pool for each malady, it's a system.

In Robin's case history, he admits to having had depression, at least according to his widow, please see the article.

That being said, he did suffer from depression multiple times throughout his life. Not saying you're wrong, just that the quote is still relevant and from experience. The Lewy body disease caused a loss of 40% of his dopamine neurons, which given how important a role dopamine baselines play in depression, it's almost certain he was also depressed, on top of all of the other hellish things the disease threw his way.

For anyone who wants to know more about his death, here's an article from his wife, published by the American Academy of Neurology.