I have never given much thought to Sherlock Holmes as a boy or spent any time pondering what Holmes must have been like as a teenager. Reading "Eye of the Crow" though kind of forces the issue.
I think the origins of Holmes that Peacock chooses are a much darker and more depressing view than I would have had. That certainly does not make Peacock's ideas wrong, just a different interpretation than I probably would have made.
The story IS dark. It shows a bleak childhood for the boy who would become Sherlock Holmes.