Allow Skipping questions doesn't work

"Allow Skipping questions" doesn't work.

It doesn't make any different if I check or UN-check the checkbox "Allow Skipping questions" on a question-edit form.

I tested this with Multiple choice question. When answering the questions and not filling in anything but just hit the Next button I get the next question. I suppose this is a bug.

How to see this bug?
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Step 1 - Create a quiz
# Admin --> Create content --> Quiz
# Fill in what you need
# Check the checkbox "Allow Skipping questions"

Step 2 - Create two questions
# Create at least two questions
# Admin --> Creae Content --> Question (Multiple choice question)
# Fill in what you need
# Do this ones more for the second question.

Step 3 - Take the quiz
# Admin --> Content Management --> Content --> Select your quiz
# Do not answer the question, just hit the [Next] button

I suppose that when the box "Allow Skipping questions" is checked this should not happen. I suppose a message that tells the user that he must answer the question.

Regards and success,
Neorg