Yes, CSSN will always prevent PBS from using the system-generated Award Pairings line.

You can prevent PBS from using the system-generated Award Pairings line in other instances as well. Take the following bid:

Prefer Off ...
Avoid ...
Avoid ...
Award Pairings If X
Award Pairings If Y
Award Pairings If Z
Avoid Pairings If Pairing Credit > 0:00
Award Pairings

If PBS can get you in the Line Construction Window (LCW) after using "Award Pairings If Z" then the Avoid line below it (which filters out all pairings) will prevent PBS from using the system-generated Award Pairings line at the end. PBS will not deny the "Avoid Pairings If Pairing Credit > 0:00" if you are in the LCW by that point. This is one technique pilots can use to prevent PBS from adding additional credit when you are in the LCW but below the Threshold. There is a PBS Notepad that goes into more detail on the Threshold and this technique:
https://dal.alpa.org/Portals/1/Docum...epad-19-06.pdf

There are other techniques you can use to do this depending on your seniority and preferences.

CSSN can get the job done but it has a number of pitfalls. It just takes one Set Condition, Avoid or Prefer Off in a bid group with a CSSN to derail the whole bid group. A frequent culprit is when a pilot uses Set Condition Min Credit or Max Credit with a CSSN. It's an easy way for the bid group to fail since you have no idea if Min Credit or Max Credit bidding will be limited (and how much) in your category. Another common failure point is not including enough Awards in the bid group. One miscalculation on the credit total or an FAR violation that is hard to determine can also cause the bid group to fail.