There are without doubt individuals on this Analogue Forum that have acquired a in depth understanding of Cartridge Technologies and are committed to the source of the designs and their minute understanding of their designs.
Another consideration is that design teams come together and separate heading off in other directions, possibly seeking new challenges or creating their own ventures, many revered Cartridges are now separate Brands from this type of historical happening.
In a more modern world, freelance is a more common seen method of recruitment, and technicians are used for a particular project, maybe in some cases to bring in fresh thoughts and rejuvenate old staple philosophies. These types of individual are gathering a broader experience and have a developing skill set that is potentially able to produce a variety of configurations for materials used on a Cartridge that will deliver a very acceptable end performance.
I use a Cartridge rebuild service that the Technician started out their career as a freelance and has worked within a design team on a few very well known Cartridges, that are very well received by a large number of users. This does not mean I am doing anything absolutely correct, it just means I am offering my Cartridge to an individual who has had hands on the early designs and production of Cartridges from the same brand, I find it quite reassuring, that the Technician is well versed and experienced in working with the Brands Technologies.
Another consideration is that a Brand will usually design a Cartridge that will be a Parent Model, and there will be follow up Models produced using proportions of the Technologies found in the Parent Cartridge.
I will suggest that this is for two reasons, One to be the foundation of a New Range of Models to be offered, and the other to produce a Sonic that covers a much broader spectrum of a listeners preferences, creating differences to assembly of materials found on the Parent Model, to counteract the deficiencies it has to meet a certain type of sonic trait.
It is common to see a range of Cartridges where the assembly of parts differ slightly, be it a differing Stylus, Cantilever Material, Cant' Material / Stylus, Damper Material, Suspension Wire, or even a slight change to the Coil Windings.
Technically these new produced models using the Parents Models Core Technologies are looking to myself, to be rebuilds of a particular model, albeit the Parent Model as being the start point.
It is also known as a disclaimer by manufacturers that if a Cartridge is returned to be overhauled, that there might be differing components selected for the refurbishment works, as the originals may not be in stock any longer. This as an outcome will be to produce another variant of the Parent Model or Off Spring Model. What is for sure is that the returned Cartridge will not be the same assembly of materials as the Model when purchased new.
If a Third Party Service with a good reputation, chooses to use a different Stylus, Cantilever / Stylus, Damper or a Suspension Wire, the work undertaken will have created a further variant of the Parent Model or its Off Spring Models. It is impossible to say if such a variant is a lesser performer than the pre worked on model. It is very possible to say the Model is no longer an identical model to the supplied model at the time of purchase, and this seems to be very similar to the disclaimer being made by a manufacturer.