It's nothing new. DT has been doing this ever since I joined them three years ago.
Agreed, nationality definitely helps them with the completeness of their records in case a dispute occurs, however, they ask for a lot of redundant information. Besides, people tend to mature, and people tend to relocate, so the use of that information is rather time bound.
All redundant bits of information about the models you use is already required when uploading a new model release. Dreamstime's explanation is, that all this information is required, because of their ingenious search options, which allows buyers to search for a specific number of models, ethnicities, and gender groups. I just wish they would make that an optional bit of information, because I found it extremely tedious to file the correct number of model releases and identify all persons in a group of 20 people dancing in a nightclub correctly. Let alone the DT reviewers know how to distinguish models by name.
In the past, I've had rejections for an incorrect gender - the default was male, and the model happened to be female, quite obvious from the photo. (DT did change that in the registration form for new models). I've also had rejections because the DT review team thought the models had a different Ethnicity than I filed with the release form. I've also had the MR for my son rejected. As a minor, my wife signed it as gardian / parent, but she doesn't use my sir-name, and my son does. It's always a guess - a few rejections have been overturned by resubmitting the same file under the same model release, or by contacting support.
It's all a bit over-jealous, I think. But it's their prerogative.
@ pancaketom: Yes, they require your signature as well. Apparently , that requirement is legally unstable, as a MR isn't a contract.