The similarity in clothes stems from the fact that the family were not ordering new clothes during the war. The Empress donated her clothing allowance to the war effort. It was not expected that the war would last so long and, as it did, the family's staff were kept busy mending and repairing. As a result, by the time the family were sent to Tobolsk, they were wearing quite old clothes, often repaired, and "dated". It also leads to confusion in dating pictures.
This could be the source of confusion regarding the picture. Also, if we knew who took it, then we would have a better idea. If it was from teh family albums, then it was taken prior to their departure for Tobolsk, which would support the dating of the picture to 1916.