Yeah that's only for the partition that contains your ISOs.
You can make another ext4 partition on it if you wanted, it just has to not be the first partition on the disk.
Oh and the encryption feature is dumb dont even bother with it
Also you still have to buy your flash drive so why not invest in something better
I never got uefi images booting properly on those grub multi boot utility drives. Granted the last time I bothered with it was like 10 years ago now since ive had multiple different iodd enclosures since then.