These pre-generated manpages are built using the Squashfs-tools Makefile
defaults with the gzip, lzo, lz4, xz, and zstd compression algorithms
selected.

The manpages are intended to be used by the installer if help2man isn't
available on the system.

But, they can obviously also be viewed by anyone who doesn't want to build
or install Squashfs-tools, by running man -l, i.e.

% man -l mksquashfs.1

Will display the manpage for Mksquashfs.