Well, you may say that the proof is in the pudding...but I don’t think it is.
That stuff is merely suggestion, with no physics behind it. Sure you can change arm action when going around a tight corner, and many good indoor sprinters do—but that’s not what this was. Yes by having balanced lateral action you can buffer the effects of lateral imbalance but if you are running correctly, that imbalance shouldn’t be there.
Neither Privalova nor Fredericks needed it to be monster indoor 200m sprinters, and Fredericks was moving WAY faster than Steiner.
Sometimes, women use the heave-ho to good effect, the last 200m great that I can remember having been an in-shape Schippers. IMO it may have something to do with front delt musculature—some women have less of it relative to pec strength, so bring the arm across to recruit more of the pec in a favorable way. You can see that both Schippers and mow Steiner had great 200m turnover maintenance, in part maybe because it takes the larger pec longer to fatigue. Who knows.
Athletes are all individual. While it his may seem to work for her, I don’t believe in the first instance their claims that it was intentional, or specifically geared to indoor racing. If she’s 21.03 indoors with that action, then she might be 20.83 outdoors. Then with a “better” arm action, she’s not 20.73 outdoors and a contender for #1.
Maybe. Time will tell. I keep watching.