Technically this is just a mutation. Mutations are quite rare, and when they do occur, most result in the organism being less fit or provide no increase in fitness. Positive mutations will increase fitness and allow the organism to reproduce more often compared to the others. This overtime eventually leads to the evolution of that population. But the evolution time scale is insane, so while this is super intriguing, we truly won’t be able to classify it as evolution for a good long while. This does seem to be a positive mutation as the larger surface area increases motility, yet only time will tell if it’s beneficial enough to replace the current tail physiology.