> I believe this is in contrast to always using the endianness of the
> machine you're on.
This is correct I believe. mksquashfs would make it for the endian-ness of the machine it was run on (it also had options to make it for the other endian-ness for cross-fs-creation). A kernel could only read a squashfs made for its endian-ness. So, the fact that it is now little-endian is somewhat immaterial, it is that the endian-ness is fixed that matters.