Does the Grand Underground count as a “dark place”?

Question

In other words, will the Grand Underground give the Dusk Ball its multiplier or will it just be 1* like a regular Poké Ball?

Comments

These things for some reason dataminers find very difficult to figure out.

Answer 1

According to the official Pokemon website, Dusk Balls have improved efficiency in the Grand Underground.

Stock up on Dusk Balls! No matter how well-lit a cave or cavern may be, you’re still underground where Dusk Balls will serve you well.

Source

Answer 2

Yes it does. It is a cave, and dusk balls have a increased catch rate.

Source

Comments

This may well be accurate, but I wouldn't take it from this source. It's a one-line response from a random person on Gamefaqs, and the Bulbapedia article quoted says nothing that necessarily agrees with the answer.