Yes, DRM-free* (notice the wildcard) is the middleground applied on PCGW for games that you can do whatever you want with post-download after the initial download, regardless of what that initial downlod might entail.
This is used for DRM-free titles on Steam, Epic, and other platforms that do not bother to give you a one-click installer.
If you want the same for Epic games, right click the downloaded game folder and hit Send to -> Compressed folder (archived).
Because the alternative is to start flagging accounts and requirements as DRM, such as the fact that you require an user account and a modern web browser to even download the installers off of GOG, not to mention that their installers themselves also have their own requirements beyond what a basic archive might have.
Basically, the DRM field is used to track the DRM requirement of a game post-download, regardless of how the initial game content was downloaded from a platform.
This middleground allows PCGW to properly account for and cover titles and lists such as this massive one of DRM-free titles on Steam: https://steam.fandom.com/wiki/List_of_DRM-free_games