versions. releases. bug fixes ... etc.
I still don't see what's confusing. The Prerequisites docs state
minimum versions, and the script downloads some particular versions
that are above the minimum versions. If you want to use later versions
you can do so. If you want a simple foolproof way to fetch and build
them without caring about specific versions, use the script.
contrib/download_prerequisites script is the simplest way to obtain
and build them.
Does that script fetch from the source sites or from the ftp site at
gcc.gnu.org?
gcc.gnu.org but they're the same packages, so I still don't see what's
confusing you or what says "NOT THOSE LIBS".