Pannier bottom attachment point

I commute with a pair of Nashbar "front" panniers on my rear rack. These
have a steel spring (surrounded by a plastic sleeve) with a loop on the end
to secure the pannier under tension to the rack. There was some sort of
"strap" across the lower portion of the back of the bag to hold the pannier
close to the bike .... long ago broke and replaced, by me, with a piece of
wire (hey, it works)

I just bought a bunch of new panniers from Nashbar that were on sale (for
this and my other two bikes) These panniers have a different attachment
system. They use a bungee cord with a hook. OK, but instead of the strap
secured at the ends they have a strap with sewn up seams dividing the strap
into 3 or 4 sections. MY QUESTION: What is the reason for these
"sections"? Is it so that I can "adjust" the pannier ... to elimate (or
minimise) hell strike ... or, what?

By the way I'm not crazy about these "framless" top loadiing panniers. My
old framed, side loading are nice, and I'll continue to use them for my
commute, and save the others for my other bikes or when I need the extra
capacity.

Richard in Boston, MA, USA