Leroux: Steam requires an online client to install the games, so you can't install the games on a computer without internet connection or if Steam is down. Call it what you want but that's causing the same problems that DRM can cause
ET3D: DRM-free, far as I'm concerned, is something that can be freely copied and run without any limitation, and that's true for these games. True, the need for Steam to download and install the game can be an inconvenience, and is certainly a reason to pick a store like GOG for people who are inconvenienced by it, but I don't think it prevents these games from being considered DRM-free.
With the ability to run the installers offline the customers can download them with any reliable and fast connected computer they can access occasionally, while the online installation requirement limits them to computers that they also have the installation rights. Also any DD game that isn't officially sold as DRM-free can't be considered as such, because there may not be much hope of getting a refund if the publisher manages to add DRM just before you have the game downloaded, installed and backed up. And with every patch the game's DRM status needs to be verified and backed up again.