Like the 20 question test better than the 5 question test
I suspect each has its purpose. A 5 question test can be a useful memory retention exercise with recently recently presented content by helping students committ the right information to memory vs content that is not as important. A 20 question test is a better assessment of broader sets of content. But even a 20 question test can be manipulated to be learning tool. By careful attention to a progressive question sequence, a teacher can build a kind of dvidiing line between what a student knows vs what they don't know. Subsequent tests would then be used to see if the student has moved that line.
I found some useful information. Some schools tend to focus on things like activities and appreciate events, award to improve retention, while communication of policies, procedures and resources falls behind as we all assume that "everyone already knows."