Good catch
The "darkness" comes into play because UX design choices are being selected to be intentionally deceptive. To nudge the user to give up more than they realize. Or to agree to things they probably wouldn’t if they genuinely understood the decisions they were being pushed to make.
To put it plainly, dark pattern design is deception and dishonesty by design.
https://techcrunch.com/2018/07/01/wtf-is-dark-pattern-design/
https://www.theverge.com/2013/8/29/4640308/dark-patterns-inside-the-interfaces-designed-to-trick-you>>6680097