The way the code works, the change has to be applied to all types or none as it's a sinlge function that processes them all (display_submission() in the assignment_base class). I tested the patch with the other types and although it's not so necessary for them, it doesn't break anything as far as I can tell.
As far as accessibility goes, I assumed that screen readers would be fine as the text content hasn't changed. I also found a comment here suggesting that overflow like this was an essential accessibility feature so that the page layout doesn't get wrecked when the font size is increased, so it may be an improvement.
Definitely agree that feedback is needed.