In regards to that four-quadrant infographic - how could Technical Reference fall into the category of "theoretical knowledge?" I'd think tutorials would fall under theoretical because if it gets too practical, are you not effectively writing a how to guide? I'm not really sure the four categories fit into that quadrant scheme as well as they'd like.
Practical knowledge is knowing how to do something - tie your shoelaces, instantiate a model class, authenticate to an LDAP server.
Theoretical knowledge is knowing what is the case - that the cross-flow valves must be closed at take-off, that everything in Python is an object, what a Python property decorator does.
Technical reference is theoretical knowledge (that you apply in practice), as is explanation. Tutorials and how-to guide contain practical knowledge.