But "classification" is the terminology. "Categorization" would be ok if we go back X many years in CS/Stats literature and rename it as "categorization". I think "categorized" would be more confusing here. In this case, I would compromise to something like "Dataset of labeled screenshots from [...]".

HN is not an audience of CS and Stats academics, or those familiar with the literature in those fields.

You don't need to be an academic to be familiar with a discipline's terminology. If you keep reading articles like OP, at some point you'll learn that by convention people use the word "classification" for things like this.

But in HN, the more common usage is government classification, so headlines should be based on that precedent.