Many OpenGL functions have special suffixes that specify the types of arguments that they take. Things like “3f”, “iv”, etc. This is here because C (and other languages) doesn’t have function overloading.
The reference manual doesn’t include those variations in its function list (which is why the function list isn’t enormous). So glGetShaderiv is filed under its base name: “glGetShader”
Oh, that’s a simple answer. :o
Wow, your Tutorial is huge! I’m sure I will enjoy it.