Did you paste the correct snippet into "Tree generated for (2):"? Looks like it overlaps, and I suspect it is the last example without the overlap-prevention.

> Am I worrying about a non-issue?

Probably not, but did the range position invariant checkers tell you about this problem, or did you notice it indepenantally? If it is the latter, why didn't the invariant checks go off? Should they be updated? Or are they intentionally weakened underneath transparent positions.?

Overall, your explanation makes sense to me.

I'd like to see some of this documentation transferred as you judge best into the commit comment / scaladoc for the new utility method / additional tests.

Almost there!