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Adblockers stop publishers serving ads to (or even seeing) 1bn web users - Press Gazette
(pressgazette.co.uk)
This is a most excellent place for technology news and articles.
You may be right, technically, but based on the context, I'm quite sure the use of the word "dark" here is intended to frame the behavior as negative. It's just like when various media authors refer to TOR as the "dark web" even though it has countless valid uses that are not enabling illegal/immoral behaviors.