I have been able to try out differentiation tags a bit, so I think I may be able to provide a bit of clarity here...
Differentiation tags, once created, can be used in the "Assign to" area to extend due/available until dates for assignments (and quizzes). I believe that's what that FAQ is referring to.
Differentiation tags cannot, to my knowledge, be used in any way for quiz (either classic or new) moderation. So while the tags can be used to extend the quiz due date for tagged students, they could not be used for something like a time multiplier or extension on a timed quiz. This could change in the future, but is the current state of things as I have experienced them as of right now.
I hope this helps a bit!
-Chris