initfs partition has its own version numbering and it can be shared between various firmware releases so version of firmware (50-2 in this case) does not matter for initfs flasher (and is not checked). The only thing that matters is content of /mnt/initfs/etc/initfs_version.

Also the flasher should always refuse to modify unknown (newer) initfs. With every new firmware release I need to check it and see if it needs different patch or I can make an alias (soft link) to any older one.