Greets from a lurker,
First, thanks to Glenys for pointing to my site.
This is slightly off-topic but is related to the multiselect type of exercise.
I also avoid using it, but once in a while it turns out useful. I'll exemplify with a screenshot at the same time trying to clear the confusion around this question type.
In this question, what I want from students is to identify the two possible answers.
Our 'poor' logic is that we (most people - and we also teach students that way) confuse scoring with logic, as it was mentioned. You can see in the screenshot 3/3 for feedback. This is because the student has made three correct decisions - a) and b) are correct i.e. possible answers and therefore checked, answer c) is wrong and therefore unchecked. The total score on the question is 100% because the student has made three right decisions.
The screenshot also illustrates how I've used the multiselect. However, if one wants to stick to the popular logic of selecting the one and only when having two or more correct alternatives, he may use Multiple choice and word his question negatively. In my example, that may have been "Which of the three is NOT correct?" and be displayed as a multiple-choice question. BTW, students need a little training how to think about and interpret such scoring.
A more pedagogically meaningful exercise is to train students to predict what they may hear in a recording or read in a text within certain context. I use it in listening and reading comprehension activities to make students READ the questions more carefully before they hear the recording or read the text. This is a modification that's not listed in my Taxonomy and requires some hacking. It looks something like the second screenshot. It's not the best example, but still OK to teach students to expect and predict from context ...
Cheers
Stan