Do not expose location. Expose name.

I would still call it DRW_UNIFORM_VERTEX_BUFFER to make it clear it is a value of this enum.

Also you could eventually bind these to other shader stages if that's needed in the future. So I would remove the for compute shaders part.

If you want to make it extra clear, you could name it DRW_UNIFORM_VERTEX_BUFFER_AS_STORAGE.

While the normal storage buffer would be DRW_UNIFORM_STORAGE.

All things considered, the UNIFORM should be renamed to RESOURCE, but that's for a later cleanup.

Get location from name here.

I would advise against this for new code. This is something that creates hard to read code with #ifdefs everywhere and it's hard to see what resources are needed.

I would prefer to see the refine functions go into a shared lib.glsl file and have a dedicated _comp.glsl file.

Use writeonly qualifier.

Not sure where this capitalization came from. :) Also unless blender became a spatial 4D app, the positions are only 3D ;). From the vertex format, I think it is posTime and would prefer to reuse it to keep consistency.

In new code I tend to prefix all the outputs with out_* so shader stage outputs are easily identifiable .

Alternatively you can name the instance of the buffer out_vertbuf like so.

layout(std430, binding = 0) buffer hairPointOutputBuffer
{
  vec4 posTime[];
} out_vertbuf;