Extensions to Khronos standards are hardly that greatly documented.

A TXT dump of the proposal, with luck a sample from the GPU vendor, and that is all.

Vulkan was famously badly documented, one only has to go to LunarG yearly reports regarding community feedback on Vulkan, and related action points.

OpenGL 4.6 never has had a red book editon, Vulkan only had a red book for 1.0, OpenCL and SYSCL just have the PDF reference, not all Khronos APIs have a cheatsheeet PDF on Khronos site.