Replacement Apple Watches are very rarely, if ever new. Apple themselves will likely tell you they will appear new, because they do receive a new display and the battery, but the casing is reused due to soldered components, which is exactly why it’s a refurbished unit.
Not sure what 'soldered components' means. I did a break down of a series 1 and all components connected by micro connectors and very small screws with some adhesives used to position the battery and charging stuff at the base.