We chose to strip extra detail out of the PEP and put in a secondary location.
I think we chose wrong. 
I’ll try to reply and point to the other material as appropriate. For example: write yourself an HTML template system.
As a note, we have an implementation that we’re gradually building to be a full-featured choice, along the lines of htm or lit-html.
Full-disclosure: I’m interested in component-driven development for Python, so I have certain bias and viewpoint. My direction is intermediate VDOMs for re-execution and caching.