I consider installation to be part of execution, as per your defs. You consider it to be part of the delivery.
I consider installation to be part of installation. Not delivery, nor execution. Steam games do not have the installation part.
GOG has DRM'd delivery (authentication required to download the files), a DRM-Free installer (anyone can run it) and DRM-Free execution. GMG (I think, it might be GG, never paid much attention to those) has DRM'd delivery (authentication required to download), DRM'd installers (online check to run) and both DRM'd and DRM-Free executions, depending on the game.
Steam has DRM'd delivery and DRM'd and DRM-Free execution. I'm not sure if there is a check required for Steam to parse installscript.vdf or not, but the file can be parsed without Steam just fine.
Sorry, misread what you wrote.
I don't see any part of any delivery system as DRM. It's all part of ensuring that an individual gets what they pay for. Otherwise, we might as well consider buying via retail store to be DRM in that you (or whoever buys) is identified as the person who paid (by visual inspection + memory of retailer) to be handed boxed game. If you were to regard that as DRM, then the only truly DRM-free games are free downloads.
Steam does install your games. It puts all the files in the right places, and installs all dependencies. That sounds like installation to me. It's simply that it does it all transparently, and it occurs during the download phase. I consider it to be a similar case to GG, which is probably where you and I differ.
Edit: Continuing the retail analogy - Steam is doing the retail equivalent of, when you pay, going home with you, installing the game on your computer, then going back to the store taking the box with him. I consider that to be an unreasonable control of my purchase - pretty much part and parcel of DRM.