They may very well have psychological inhibitions or real fears of physical violence in terms of coming forward, but I think you could say that about any criminal behaviour. I think you could also say that about spousal abuse. It's not a reason not to enforce, whether that be criminally or through the immigration system.
One thing that's interesting is that in the administrative immigration system by which something like this would come forward, the rules around those types of hearings are very loose, because it is an administrative process and not a criminal process. I've never seen a case where they, for example, offered the victim a chance to testify behind a screen or not have to face the abuser in the same way that they do in criminal court. Maybe that's something that the board needs to consider.