This doesn't surprise me at all.
Mainstream "Christian" and the definition of "Christian" according to the congregationalists, nazarenes, etc is somewhat different. Not that this bothers me any; I'd have thought that the families looking to adopt would have done a bit more thorough research into the mission/regulations/doctrine of the private group they were trying to adopt via.
Adoption is very difficult in the US, from agreements by African-American social worker groups to not place black children with white parents to things like the above. This is why so many are currently adopting from China or Russia. (Personally, I know of 12 families who have gone this route.)