From the article:
Two years ago, he took on a 16-year-old as his bacha. The relationship will end soon, he said, sitting next to his companion, Jawad, who is now 18.
"When he starts growing a beard, his time will expire, and I will try to find another one who doesn't have a beard," Assadula said.
This is the religious rationalization. Boys are not men; thus the relationship is not homosexual. In Islam, homosexuality is considered a crime against god, punishable by stoning to death.