According to this question: Questions from ru.SO shouldn't become hot entire ruSO site shouldn't become hot. But I just saw the following while searching MSE:
Direct link to the question on ruSO: local storage : Uncaught TypeError: Cannot set property 'innerHTML' of null
Perhaps the HNQ filter works on question title (in the current case there are no non-Latin symbols) instead of site origin. Hence, according to the post mentioned before this behaviour should be interpreted as a bug.
However, I suggest to fix such "bug" by taking another feature request in mind: Include non-English websites in Hot Network Questions, based on user's location/language/IP