That's like Theseus bringing in his ship for maintenance and when he returns to get it, the ship mechanic saying "so I have good news and bad news..."..
Probably because they pack a ton of files into a handful of compressed archives, which means the full archive needs to redownload when a single file is changed. Does Steam not have a delta patching system to handle this? They already compress downloads so it's not like a delta patch framework would cost extra CPU in comparison, and the bandwidth savings would be immense. Seems like low hanging fruit to me?
They do have delta patching, but it's pretty useless for some types of compressed archives. A single changed file could completely change the remainder of the archive's contents due to different data in the compression buffer.
I totally understand that they wanna get it right before they exit beta. When's the game gonna release and no longer have to replace all files every two months?
The game has been out of beta and in public release since the beginning of August. The changes they're making at this point (at least the hot fixes) are relatively minor at this point. But steam handles all of the updating process so if you've got massive updates that's more on them than on Larian.