Because that’s a generic version of the camera body (in many cases, a grouping of like models - not specific models) - - and not necessarily exactly the same as any specific camera’s actual rendering.
See here for more on this - - Note the observation by @Egregius/Greg.
John
Edit: I’ve just encountered an actual case-in-point (reinforcing my point);
- I have a Sony a7 iii
- The rendering group for this body was the “Sony a68, A7 III ~” group - but, it’s been moved !!
- It’s now in the “Sony A7 III, A7C” group … this probably happened with the recent 4.2.1 update.
- Now, the rendering for the “Sony a68, A7 III ~” group is very slightly different from the “Sony A7 III, A7C” group … and this new model-generic group is actually more accurate than before (I can tell this because it’s the same as Camera Default Rendering).
Edit#2: The grouping for my Olympus OM-D E-M1 III has been moved around too - also with results (for the new grouping in which it now resides) now closer to the actual rendering for this body.