The description of the dry wall shims found at the site referenced
below contains the following statements.

"Ideal for floating butt-joints and framing irregularities. Save time
by shimming drywall to allow greater inset at joints. Ensures maximum
bonding of tapes with drywall."

http://www.amazon.com/Strait-Flex-Dr.../dp/B00236E27Q

How would these shims help with "floating butt joints", which I assume
are butt joints not centered on a stud?

What do they mean by "allow greater inset at joints" and how would
this "save time"?