We quit using New Quizzes because we could not control the visibility of the answers of all assessments if we allowed the students to see the results after their assessment. Once it was on, we had to manually go to turn off the feedback. Either it was on permanently or we had to manually turn it off after they viewed it. This is a very strange error. Do you know if this issue has been fixed?
We aren't always aware of what bugs have been reported. Did you or someone from your institution file a support case for this behavior? Generally the best way to be aware of the status of a fix is by submitting a support case, as you'll be notified with any updates.
As a followup question, were you receiving an error when you changed the setting? Or are you inquiring to the general behavior of whether or not there will be a feature change in allowing students to only view feedback for a specific amount of time? For the latter, I did find related feature ideas you may be interested in following: