It's possible for both things to be true. Human reviewers might be biased towards awarding higher scores and the computer could be dog shit at scoring. I have no idea how this can meaningfully be grading fluency. Fluency in a spoken language consists of vocabulary, grammar, and pronunciation.
I have seen plenty of people who were very fluent who speak with an extremely noticeable accent who were none the less comprehensible. Software is extremely likely to perform poorly at recognizing speak by non-native speakers and fail individuals who are otherwise comprehensible. Because it wont even recognize the words its nearly entirely testing pronunciation and then denying such students access to electives that would allow them to further their education.