Correct, but GOG provides games without _any_ DRM, both in the installer and in the game itself.

The whole reason for GOG existing was they strip dead DRM from old games so the work again without "warez scene" cracks; and fix all the OS/driver incompatibilities along the way.

As far as I know all the games you can buy on GOG will be completely DRM free.

> What does the installer matter for DRM-free software?

Requiring a network-connected proprietary client to install the software is itself a form of DRM.

> For software with other forms of DRM built-in anyway, who cares if the installer has it?

Again, GOG does not distribute games that include DRM, whether in the installer or in the game itself.