@twinklecake I know what you mean and I think there will be mentioned more about that part. But since he showed so much knowledge so far and states they can't be heretics since they carry the cross with them, there is obviously something to it.
They have the same cross and it's obviously shown there is more to it than just it's look.
I think this is just the first hint and info, instead of bombarding tons of stuff. I mean at the end he asked and the the girl even answered properly about the other god whom she believes in.
Not getting bombarded with all kinds of random info is probably on purpose. We don't know too much about the crown system, too. Which even those other guys at the end knew about.
I think when they face the heretics is when we get the info why they can't wear the cross or more info about the gods.
If not, well.. it's a cross, i guess ? Reason enough