Doesn't angle of the cantilever change anytime it moves from side to side, meaning, anytime it reads a lateral modulation? Same for up and down and vertical modulation
Also, if the stylus is riding in the groove, reading audible signal, how can it draw a high-amplitude 10 Hz sine wave on top of that? Unless there's sine wave of that amplitude embedded into the groove I can't see how it could do it, there should be no space for the stylus to do that.
At this point I'm even convinced this 10 Hz high-amplitude component isn't really reflecting what is happening in the groove - maybe the tonearm wobbles at 10 Hz relative to the stylus in the groove, and this movement induces current in the cart. Even though we want only current cause my movements of stylus in the groove, we can't get it in isolation, since everything moves and interacts.
Why would we care about pressure on the surface if MM/MC cartridges measure velocity?
Basically you said "it wobbles at 10 Hz and it affects other wobbles at other frequencies". Sorry, but this doesn't seem a convincing scientific argument. In essence this is a statement about a tonearm/cartridge system being a nonlinear signal transducer. 10 Hz affects regions far from 10 Hz. While it makes sense, none of the above explanations say anything about the amount and inner workings of this nonlinear behaviour.
I hope somebody could give an explanation in terms of transducers (I guess cartridge could be called a seismic transducer?)