This is paraphrasing here but the phrase they used is "coming into Islam by oneself." The implication being that it isn't recognized if he does it because he wants to marry this woman, it has to be of his own free will. It's really weird to me because I never even knew Islam had those rules about marriage. The only other Muslim I am sort of close with is a lot older and married a Christian woman with no major problems - she converted. My opinion as a kafir is the woman should make her own decisions based on what she wants - what's the point of religion if it keeps you from being happy? It just seems wrong to me that the family would make the guy jump through all these hoops when he's already very accepting of her beliefs. If he wasn't, why would he be willing to convert? That's life I suppose. Not much to do other than try to understand.
Ah, coverting to islam, or being Muslim for convenience's sake. I think I understand now. Muslims believe Islam is the truth, if you don't believe that Islam is the truth, you are not Muslim. Makes sense, no? The belief part comes before everything. A person -so to speak- stands alone.
and if you think the point of religion is to be happy, then that is another subtle but significant difference. To be Muslim, you got to believe it's the truth.