So a Sikh girl can marry a Hindu boy, but then he has to become a Sikh boy? Otherwise marriage becomes null and void?
YES- that's what it is.
The anand karaj is only permissible if the boy becomes sikh. This doesn't mean that he just dresses up in a turban for the day (like so many have done in the past) , this means that he takes amrit and becomes amrithdhari.
These are the rules, no ifs and buts.
- Otherwise, there is nothing sacred left about anand karaj.