If I understand you correctly, I’m afraid I disagree. Please review the examples in the top post after my most recent edit to see if it makes more sense. I still need to create the step-by-step diagrams to make it clearer (vs. the current wall of text) but hopefully it’s still reasonably clear.
What you’re calling the “head-final” I’m calling the “core” of the sentence. It’s possible to have extremely complex sentences with multiple clauses, but only one can be “core”. I do agree that the diagrams need to make the “core” obvious, and everything else should branch from it.
I’d also call what you’ve drawn sentence diagrams, not tree diagrams with noun-phrases and verb-phrases indicated. I thought tree diagrams looked like what was discussed in this thread. I find these difficult to understand because of the additional grammar jargon.
I should probably stop harping about how much of a beginner I am. This point, for example, I think I learned in 1977. I still consider myself very much a beginner with Japanese and grammar in general, but everything is relative. (I know a lot more than most of my relatives on the US side.)