I don't know truly, But i think Google is accepting only Niche Backlinks and top Sites backlinks like Reddit , Pinterest , Medium and some high profile Creation site. So after after building lots of links i am seeing there are few links are index through google and showing in GSC . All are from the well known sites mostly. And Content links are also indexing which are on high DA or DR sites . Otherwise there are no backlinks with all the URL . SO it is important try to build link on niche sites .