It is my understanding that the poor tension maintenance in natural gut is common knowledge. And while pre-stretching IS to get rid of coil-memory, it is also to help curb the loss of tension that occurs immediately after stringing. Being one of the most elastic strings out there, gut is inherently poor at maintaining tension. What it doesn't do, under normal conditions, is become "dead" as quickly as other strings, but this is not the same as maintaining tension. This is where the positive feedback comes from. The tension has been lost but the string still plays well because it has not become "dead" like most synethics become over time.