Do you have a source for "no plans on adopting Vulkan"? Apple is definitely on the Vullkan working group (logo is part of the image at the bottom of https://www.khronos.org/vulkan).
Why adopt Vulkan given their investment in Metal, to the point that they have moved their accelerated 2D stack to Metal.
What is the point to rewrite it again for Vulkan?
Even if they adopt Vulkan, most likely would be a layer on top of Metal.
As for being in the group, Sony is also and they don't use OpenGL on their consoles.