While the Parnassus and Olympos share the same magnetic circuit, that's the only thing that they share. Everything else is different.
The stylus shape is different, the cantilever material is different, the coils are different, the dampers and suspension are different, the mounting of the cantilever into the cartridge body is different, the body shape as well as material is different, etc. The cartridge mass is also increased, which means that the tonearm interaction will be different. In my experience, every one of these factors will affect the sound, and not necessarily in a small way.
Neither was it ever my intention to make the Olympos into a cartridge that sounded particularly close to the Parnassus. When I revisited the Parnassus (after having the experience of the Parnassus DCt, Helikon, Titan et al), there were a few traits about the sound that I continued to find delectable and felt were worth carrying forward, but there were many things that left much to be desired, particularly in the areas of tonal neutrality, dynamic range, immediacy, transient impact, frequency extension, detail retrieval, soundstaging and image focus, and the sense of a solid "core" or "backbone" to the musical performances. The Olympos was designed specifically to overcome these weaknesses of the Parnassus, and bring it closer to the performance standards of the best cartridge that I knew of at the time (the Titan), while retaining the particular sonic aspects of the Parnassus that I still found attractive.
I agree that the choice of magnetic system has a noticeable effect on the sonic personality of a transducer, and to my ears, the Platiron magnet sounds more or less like a super-alnico. If you like the sound of alnico magnets, chances are that you will adore the sound of Platiron magnets (and chemically purified iron polepieces).
However, the magnet is only one small part of a transducer's design. To focus on that point, with the exception of the Olympos, the current Lyra cartridges all use the same magnetic system (although the material of the core is a little different on the Dorian and Delos as opposed to the Argo, Helikon, Skala and Titan. So these cartridges all sound like close siblings to each other, right? I don't believe that I have met too many listeners who claimed this (hardly any?), and to my ears and in my audio systems they certainly don't sound similar.
However, it appears that it is possible to put together an audio system which minimizes the sonic differences between the Parnassus and Olympos, so as with most things in audio, YMMV!
hth, jonathan carr