Hello @DrB_OT ...

Within the Differentiation Tags • FAQ - Instructure Community - 639336 that you referenced above, I think you are referring to the question and the bullet points for:

What are some examples of how I can use Differentiation Tags in my course?

• Create a tag for students who need extended time on assignments.
• Tag students who prefer visual learning materials.
• Tag students according to their interests for project-based learning activities.
• Identify students who might benefit from extra support or challenges.
• Use Tags to segment students for moderators/graders.

I've highlighted the first bullet point above as it says you can create a tag.  In my opinion, this is different than actually extending the time for a student.

There are a couple New Quiz Guides that I'd like to direct your attention to (which you may have already checked out):

• How do I moderate a student's quiz attempt in New Quizzes?
• How do I add accommodations for a student in New Quizzes?

I hope this helps to clarify things for you.  And, I hope these Guides will also be of help.  Sing out if you have any other questions about this.