Papeetepatrick, in my opinion, the ballerina doesn't actually have to lower her arm slowly so much as calmly. One can be both calm and swift, and in addition to the practical concern of staying on pointe, there is also that of the music, which has to be slowed down if she is going to raise her arm to 3rd because it takes more time to get to that position, and also she will need more time to prepare for each balance. If we add to that the prescription that the arm must move slowly up and down, the music would be a dirge! I do think that the ballerina with the calmest, most regal movement in this section is Sizova. Her movements are not really slow, but there is a secure regularity to them. The arm goes up, the arm goes down, without any hint of either insecurity or showing off.
Hans! I got around to the pleasure of watching this again, and all three times are different. And it's as much the movement away from the suitor's hand as it is the often too anxious movement back. With Sizova, there is never the anxious movement back to the next hand, but on the first one, I thought that even she began with slightest nervousness as her hand left the first man (but it works when this only happens once!). Then with the second, she becomes more confident in both moving up and back, but it's the third which is so impeccably self-assured and at totally commanding ease that just knocks you out. And, although the Fonteyn you linked to a few weeks ago is no longer available, I didn't think she came even near what Sizova achieves here: The movement in a few seconds (perhaps twenty?) from slightly nervous to serenely confident is one of the most incredible achievements I've ever seen, because it works physically in such a way that there is no separation from the physical, the musical, and the dramatic. Paul had mentioned the 'she has to become the queen', and here you see her make the transformation in these three movements of the arm, which may themselves make the balance have three different and progressively stronger 'personalities', even though it is itself almost stationary (correct me on this, I imagine, there may be slight movement with each hand change, but it's hard to see on film), but it surely has had to grow in strength and confidence, and the arms may both lend strength to them and their growing strength also allows the arms to really flow. In fact, by the 3rd one, there is not even the slightest speeding of the 'dancer-music', because there doesn't need to be any further consideration given to security. So I agree Sizova's is by far the most regal, but I also think she really does not do them so much 'slowly', but does not speed against the music, and progressively becomes exactly bonded with it. It's really been worth it to concentrate on this single moment, because it's very brief the transformation Aurora makes, and the initial first slightly nervous move away makes the 3rd movement up and back this kind of miracle.
Edited to add: I just watched it yet again, and the 3rd time the hand comes back down, Sizova really does take a little extra time, a kind of leisure--and that has the effect of making you even forget that it's a balance going on. Oh, MAN!!! she had what it takes.