It’s not common knowledge even among immigration attorneys it’s very niche. As an intern I worked on one of these and saw the process the parents didn’t really abandon the kid. They sent him to work in the US, but the charity I worked for drafted up the papers stating they were not going to take him back and gave up all paternity rights. They signed the papers and then we got him into family court to declare him abandoned. Aunt got custody of the kid (17, not really a kid) and we got him a green card eventually after I stopped working on that case.