Previously it was stated that it is intentional that Asajj doesnt have SITH tag. Now, she got a prestigious event called 'SITH AGENT'. The requirement is partly to defeat jedis. The thing is that As...
Asajj was never a Sith. She was an agent of the Sith. And yes there is a difference. Think of her as an entry level employee, heck maybe even just an intern. The only people who got the Sith title were middle and upper management.