I would tell you that learning OpenCL is currently a waste of time when it comes to game programming.
I think this is a very bad advise.
OpenCL is the easiest way to do and learn GPU compute - you need one line of code to upload to GPU memory, with Vulkan you need 50.
Same ratio for the simple thing of executing a kernel.
OpenGL compute shaders are also a lot more cumbersome to use than OpenCL,
and at least in the past OpenCL was twice(!) as fast on Nvidia, and a bit faster on AMD.
You would not make such a statement if you would have taken the time to test this yourself.
OpenCL is not popular in game dev, but that's simply our own fault.
AFAIK SpirV is core with OpenCL 2.1, NV is at 1.2, AMD is at 2.0.
Only Vulkan really uses it now, but no one writes SpirV directly - it's just intermediate byte code used by compilers, so not relevant for learning.
Feature wise OpenCL 1.2 language and GLSL are very similar - anything you learn can be adapted to the other easily.