I don't think there is any link between marriages of convenience and arranged marriages.
The officers working abroad work within the local cultural norms. They understand the local cultural norms. They often have very specific training about local cultural norms. There are many relationships that go outside local cultural norms and are perfectly genuine, but you have to work within that context.
Arranged marriages, in our experience, are not particularly a problem from the point of view of determining whether or not it's a marriage of convenience. You have marriages of convenience detection challenges in cultures where you don't have arranged marriages.
When one is adjudicating the intent of the parties concerned, it is being done within a local cultural framework to the best of one's ability.
Detecting marriages of convenience clearly, I think everyone would understand, is not an exact science. It's a judgment call.