>=sys-fs/squashfs-tools-4.0 need a 2.6.29 kernel or newer to work. Newer kernels cannot mount v3.0 squashfs images. If you upgrade to new kernel and squashfs version, you cannot create an image to be used on an older machine. squashfs-tools need to be slotted to enable producing old version squashfs images. Reproducible: Always
This would require having the ebuilds rename the binaries and then providing a way to select a "default" one. I have no interest in doing this, and it's really not worth the effort.