Where did you find that?
I had no updates for a year after the test, so I asked them if my case is non-routine. They told me that everything under 23 months is considered routine. I have 21 months so far.
Of course, could be that the person on the phone has no idea what she is talking about.
It's written very clearly here, but when I said this to the Customer Service Agent, she said she is not aware of any such thing ( so much for the official website). It's essentially a very random process and they would always tell you that the average time is 23 months ( so don't disturb us). I have called 4-5 times and I think I need to stop before they put a note in my file.
https://www.canada.ca/en/immigration-refugees-citizenship/services/canadian-citizenship/become-canadian-citizen/citizenship-ceremony.html