A valid question that I always ponder! TMO should list exactly what changes in their updates, no matter how insignificant. Like how my calculator icon changed from green to blue after July's update.
I was also searching for information on the G920TUVU5FQK1 update. My phone started downloading the update almost a week ago. I canceled the download and have been searching for information on the update since. I recently found G920TUVU5FQK1 update information on the S6 Edge page, and it's finally available on the S6 software updates page. TMO, can you please list information on updates BEFORE my phone starts downloading them?!
I went ahead and sent an ask out to see if I can get more info on exactly what was involved in the update! Because we don't actually craft the updates, rather the manufacturer does, we are limited to their notes in most cases, but I will be happy to see if there is more info on this particular update available somewhere!