No matter how many times I try, I cannot figure out which of the three sections are "the two middle ones."

Probably an "anti-theft" measure.

Is Hot-wap pcb only available with E-pink case?

So your example of a "consistent, meaningful change year-over-year within product lines" is to compare two phones that are nine years apart and from two different product lines.

Seems a bit of a reach...

Depending on your definition of "meaningful."