Why do some MA styles have 'optional' techniques and perks?

[Bruno]

It's not that all of the techniques and perks are optional in the sense that you don't have to take them to be a stylist, they're "optional" in the sense that not all schools using that name teach them or teach them to all students.

In other words, they're style variations as taught that aren't big enough to really consider an entirely new style writeup.