I think that I understood better after reading those pages how what is called "Graphics Subsystem" works on OS/2. And I also think it applies to OS/2 Warp 4.5x and eCS as we have it today.
The graphic helped me to understand how to organize it referring to an architectural view.
I will think how to reorganize the GRADD and Video Subsystem pages of the EDM/2 pages.
Here it goes, corrections are welcome.
(Correction, I just updated the graphic, there was a horrible mistake)