Your LBS adheres to the catechism that sufficiently greasy chains ward off dirt and trap it in the grease so it can't penetrate into the area under the rollers. Chain wear occurs when rollers and pins wear away, the hole in the rollers enlarging and the pins grinding away. In this mantra, solubilizing the grease allows grittty stuff to penetrate the roller/pin space and thus accelerate wear.
The initial chain lube is pretty sticky stuff meant to preserve the chain more than lube it, though it does do so. It is sticky enough that it accumulates a thick layer of road debris in short order and is hard to clean off so most advise
removal of it and replacement with bicycle chain lube. It is a dirty job to clean a chain with a brush "til it is shiny". If you have the time and inclination, go at it. Many of us prefer the speed and efficiency of clamp on chain cleaners and citrus based degreasers and believe that dirt will penetrate no matter what you do. Steve