I really do appreciate your help in this matter.
What I ment was more a technical element, a method like bearing the second wheel after the rotor on balls.
Yes, you are right about technical formats changing and also about materials used.
And also that there is no reason to change if it works, but: I do see Patek's method to use for a micro rotor
a second ball bearing as a very reassuring move to show, to the technically interested, that there is something to "balance" the fact that it is a micro rotor.
I am sure that a "balance" is possibly not really needed in movements of this caliber.
To be honest: It all came just recently to my mind and I can not say if Universal Geneve is using a second bearing for its micro rotor movements, or any other maker than Patek.
Thank you again for keeping this topic alive and for your help to find an answer to this question.
Best
Moritz