I'm confused about this sentence in page 12 of the book "Grid Systems: Principles of Organizing Type":
This relationships is weak because the interior alignments are minimal
Is it because the edges circled with yellow aren't in same line?
This sentence is making a comparison with the previous image and is related to the description in the top paragraph of the book page.
It's true the terminology used is somewhat complicated.
In other terms, what it's trying to explain is the more axes of alignment there are on a page, the stronger the composition will be since the objects seem to have a firm support. It has no any relation to the end of the text frame, the yellow ellipsis at the question.
Actually, looking at the gray elements of each image they are exactly the same. Having just an edge axis the interior alignments are minimal...: there are just five red support points, while the left image with two axis has eight.
The example of a single axis in the left edge is initially weak for two reasons:
Try to see it as a shelf with vertical supports, which of both has greater stability?