The advice to not learn Vulkan first is actually pretty good, because it aligns with most people's goals when learning. Most people want to get some graphics on the screen and maybe understand what a shader is, how meshes are represented etc. OpenGL has less friction here, and I'd argue that you can learn a lot of this starting in a higher level environment like Unity, writing your own shaders and creating procedural meshes. This advice comes from the same place as "if you want to make a game don't write your own engine", which is probably works for most people.

Vulkan is great as a beginner if you want deep understanding of the graphics pipeline and are ok with some pain and confusion and a lot of "boilerplate", which comes from Vulkan having few defaults. Its a good representation of how game engines tend to use graphics APIs vs toy applications, academic projects and indie games you might see as smaller scale examples. As a beginner and a hobbyist you probably don't need Vulkan or DX12 for anything you'll build and you'll quickly be exposed to a lot of concepts you won't really understand, but I think sticking with it will give you a level of understanding much deeper than someone that dabbles with OpenGL.