GOG makes their own patch installers, and always has. They have also always been slower than Steam. It is usually only a short delay, though, and they are doing much better with D:OS than Dragon Commander (which admittedly was one of the first new release games that GOG had to deal with frequent patches for).
I experienced the mess with Dragon Commander updates on GOG first hand. So far, I do not see signs of improvement for D:OS. The 1.0.51 patch broke the installation if you had 1.0.47 installed and the 1.0.53 patch is AWOL so far.
Why not integrate an in-game updater for all non-Steam versions and be done with the headaches?