Thanks for the feedback. I created MDL-37746 for this.
All short answers are marked wrong (gradedwrong)
The shortanswer code also checks that Normalizer is present. The issue is that even when it exists, it may return null "When an error occurs". The only clue we have is that, according to one of the user comments on the docs, input that is not UTF-8 may be an error, but it is not clear.