By using the dates we have 1. a distribution over folders/time 2. a humanreadable approach.
"especially if files will be linked to multiple times on later dates."
No, the folder is set only regarding the upload date. The upload folder will hold subfolders for years, e.g. 2016, 2017, etc. which again hold months 1-12, which hold days. Example: 2016/01/30/filename.jpg (which is loaded/referenced by qa_blobs by a blob id I hope).
The current approach is IMO not good at all from a human POV: 1. Not readable. 2. Not understandable (folder structure).
I like the current approach of number ids. Do not keep the filenames. I am not even sure if the Google bot cares. It cares more about the alt tag.