I noticed, after checking this question, that when one uses the Filter to find questions with not accepted answer(s) returns both: questions with no answers and questions with not accepted answers.
For example, in the following picture returned both: question without accepted answer and question without answer.
While the output is logically correct, I think this wasn't the actual expected output. Notice the first section of the Filter Filter by ´No answers´ and ´No accepted answers´, I think that the later is supposed to filter out just the ones with answer(s) but not accepted. And the former is supposed to return questions with no answer(s). These two options are matching on the ´no answer(s)´ and I think they should not be matching.
Although this can be mend by using the techniques mentioned here.