The blog post seems to specifically answer this question far better than anyone here could. It essentially formalizes a workflow like the one you describe.

Remember than anything GH does “can be done by email”, to cite some early commentary. But collectively, the ease of use, and defaulting to best practice, that GH introduced have vastly improved and enlarged the open source community.

I know I never submitted patches in the 10+ years in the industry pre-Github. Now, barely a week goes by without at least one PR.