Okay - it's a thread from January. (I've decided to wear my glasses when in this forum so the old eyes can see the small and faint print that gives me the dates.)
Listening to the very top breeders in the late '60s to mid '70s, they advocated both line breeding and in-breeding, but they also advocated "ruthless culling", which meant they would spay or neuter any offspring that didn't improve the breed. These are folks like Becky Mason (Bel-Tor), Jean Lyle (Wycliffe), my very close friend Dr.Jacklyn Boyd Hungerland (DeRussy) RIP all three. I remember Jacklyn spaying a bitch that had a genetic (we think) problem suddenly show up after she had her Championship AND had had a litter. Of course she made sure no dog in the litter reproduced.
When breeders speak of their "line" it means that knowledgeable Poodle breeders, judges, etc can recognize their dogs without checking , i.e., "That's a Wycliffe dog, an Espree dog, a Graphic dog". I have never seen anyone achieve that through random breeding, no matter how high the quality of the dogs. Predicting the results is difficult enough in line breeding, much more so without a strategy.