GOG is extremly slow on passing on updates.
I speak from 5+ years of experience as one of thier customers.
Standard Delay :
3 to 8 WEEKS, if your lucky!
If they mess up the patching process for the "downloadable installer", they don't fix it.
And you, as a customer, have no way of letting them know they need to fix it.
Example : the game "Evil Genius" sold by GOG
Claims to be patched to 1.01
They ship version 1.0 ( No DRM ) .exe with all the other files version 1.01( ??? )
So,
A standalone ( patch / patcher ) direct from Obsidian would be ideal.