"So, it's like the Angel Island of HK?"
Actually, there are plenty of sparsely populated islands in Hong Kong they could have used. But The Lady MacLehose Holiday Village "has an air of tranquility and presents a charming view of the woody hillsides." What could be nicer.
https://www.lcsd.gov.hk/en/camp/p_lmhv.php
Using uninhabited outlying island to house people with contagious disease is not something new for HK.