That said, it has to be structured so that it's really clear that those "explanation bits" are optional reading for the curious which have the knowhow to understand them

Yep, totally. This past year I spent a lot of time setting up an LMS with content.
I included sections that were tips, good to know, for awareness, etc.

Maybe only 1 out of every 20 users might expand the section, but if they do then there is a clear explanation of why this particular thing functions this way and how to make it work in alternate usecases. Images and explanation, before and after, etc.