DRM has a clearly-defined meaning and diluting a word's meaning the way you're doing makes it less useful.
Nitpicking on whether particular title is formally not affected by Steam DRM is pointless, since Steam doesn't care to make it easy for you to discover it. At most it can be considered a bypassing of Steam's DRM in that case. It's enough for me not to use Steam at all anyway. Their whole attitude is way too pro DRM to excuse it with existence of some defacto DRM-free options there.
Please understand that I'm not defending Steam. I wouldn't let that garbage within 10 feet of my PC.
My point is that, if you call "no standalone installer" DRM, then you can make a case that the Windows Registry, pre-web-download era Desura, broken installers, and many other things are DRM.
There's a difference between DRM (an active measure to limit how you can use what you've paid for) and a decision to use certain technologies which complicates user freedom as a side-effect.