In the announcement yesterday, I mentioned the default behavior of the new Question Part Score feedback option:

"By default, your assignments will have the new Question Part Score checked for before or after the due date. To keep your students from knowing the question part scores, just uncheck the Question Part Score feedback and save."

The WHOLE TRUTH is that Question Part Score was only turned on if both Mark and Detailed Score were turned on.

So, for assignments with the Mark and Detailed Score turned off, the new Question Part Score feedback was left off.