It's been a long while since I had to get involved in any HR related business practises, but I've got a vague feeling not hiring a candidate on the basis of a psychometric test might actually fall within hiring discrimination, if it's a case that the test is unsuitable for the candidate. Which in this case, as a non-native speaker, it seems very much like the test wouldn't be a fair fight. They simply cannot complete the testing in the same way a native speaker would.