Looks good to me. Could just be perception? Maybe a slight strength imbalance? Is the swimmer right arm dominant in life generally?
Anyone that's every tried left foot braking in a car will know that proprioception on your weaker (or less familiar) side can vary greatly compared to the side you use more often.
I typically breathe to my left when swimming as it feels more comfortable to me. Breathing to my right feels odd and less elegant however my old coach noticed and video showed that when I breathe to my perceived weak side my stroke and breathing is actually better! Weird. Can't trust those senses sometimes!