If the Cantilever Material is identical and the selected Styli is identical as the OP is suggesting as being their assumption ?
If it is also assumed that a Cart' made available from either of the mentioned services, 'Third Party or Manufacturer', is in a very similar condition to each other ?
One variable that would most likely have a impact on a Sonic that has been attractive, is if a Styli is bonded to a Cantilever.
The Sonic could altered, by the material chosen to attach Styli, and the mass of the material used to produce the adhesion for the Styli attachment.
When looking at a few of the Third Party Services who are willing to post images of their work, it can be seen their is a willingness to use what appears to be a increased volume of a adhesive substance.
Styli that are viewed as a supplied part as a pre assembled Cantilever/Styli from a Parts Supplier, does not appear to have a Volume of adhesive applied that looks to be with an excess visible.