I'll wager it was uploaded at on that date, not necessarily taken.
Which is easy enough if the WG or Segei had an old profile that was taken down.
IMG_20190806_013520.jpg is definitely a standard file name used by some digital camera's but also some scanners. When the image is created the file name is generated stating a date and time stamp, 06.08.2019 and 1.35 am and 20 seconds in this example. The date and time stamp used would depend on what they were set to on the device used.
Photo's uploaded to AW display the file name used on the file at the time of upload.
Usually that would indicate the photo was taken at that time and date. However, the WG or the Sergei could have been sneaky and renamed the file before uploading it. Some of them are wiley enough to know we look out for this sort of thing.