kalirion: I wonder if he means download pre-download pre-ordered games before they're released, and they'd unlock on release date?
I think that's too much like DRM that GOG doesn't support.
No it's not and GOG has done it occasionally. I know there was a pre-load for the Witcher 3 and think some other games. All they did is give you most of the files but leave out a few so you can't play until release. Nothing to do with DRM.
It's rare, but it has been done on GOG. I expect GOG may use it more once they have expanded their back-end services for Galaxy which are are being worked on now.