It doesn't eliminate the memory, it relocates it to the analytical portion of the mind where it is available for recall.
In the reactive mind it works like a stuck keyboard key.
And not always in a rational way.
Were the reactive mind rational it wouldn't cause problems.
Instead it equates all with all, and when enough similarities trigger the reaction the reaction can be irrational, or it can be the perfect thing at the perfect time.
The reaction is kinda random in that it can't be rationalized, only reacted.
So, if you have good responses trained in, you get a good response.

The aim of auditing is to reduce the charge on the earliest traumas first because later similar traumas work as a lock on the first.
But, some are occluded and require later charges be first reduced before the main engram can be accessed.
This is better covered in Dianetics, it discusses auditing more in depth than SoS.