If you made an app just for white Christians, as a non-white non-Christian I'd be fine with it because it saves me from having to a) look at their profile, b) potentially get matched up with them, and c) waste my time. Chances are they want someone who shares a lot of their same beliefs and more importantly want someone faithful to God.

Like it or not, people have preferences.

A few year ago, I joined Match. You know how many of my 'matches' explicitly stated they don't want to date my ethnicity and only want to date their own? A lot.

Then I joined CoffeeMeetsBagel. And while I never explicitly mentioned a preferred ethnicity, they kept matching me up with women of my own ethnicity despite the fact that 50% of the people in my city are not my ethnicity. Again, how much of that is women explicitly stating they don't want to be matched up to men of my ethnicity?

My point is that even though some apps have a generalized population, the idea of intermingling is a minority. In the U.S. I think interracial marriages are like 10% of all total marriages. And religion has way more differences in terms of life style and philosophy than ethnicity.