They did not unbundle games and their DLCs.
DLCs still come in the same box as their games.
They unbundled collection games (e.g. King's Quest 1+2+3) into their constituent games (in this example, 3 boxes).
They unbundled episodic games (e.g. Heores Chronicles) into their separate episodes (in this example, 8 boxes).
It goes without saying that they did it in a most inconsistent way.
The reason for the change, so they claim, is because "we" asked for it. The best "we" could come up with to support this claim was finding a wishlist entry with 17 votes on it.
The more credible belief is that it was done for Galaxy. The fact that Galaxy is optional is not really relevant, because even if Galaxy is optional, nobody said that its side effects are optional.
The unbundling is not optional, at least not at the moment, and, quoting Ciris, "There'll be no further grouping at the moment enforced by us".
Also, according to Firek, there are at the moment no plans to fix the numerous "non-critical" issues with the existing user accounts because GOG is working on a new account system, so prefers not to bother with the deployed system. The release date of the new system is unknown (but you can buy an "account pass" if you want). That said, behind the scenes some of the more annoying issues are slowly being addressed.
Hope this helps.
P.S. No, I am not bitter. I am sweet.