Is it necessary to specify the partition type?

The discussion is basically correct. You don't really have to specify a partitition type (in Linux!) to format a partition with mkfs. However, it is still a good practice (based on experience) if you want to not make a sloppy error some day (like accidentally formatting an LVM partition because it was not labelled as such etc.) I like to be able to type fdisk -l /dev/sda and see what each partition is for -- linux, swap, lvm, vfat etc. Good documentation and bookkeeping