Yes, they are two ways to refer to Mycobacteria avium. In early days, the main variant they identified in the lab was Intracellulare, so it was referred to as MAI. Now, over 200 strains are known (only a few infect humans) so it is referred to as Mycobacteria Avium Complex (MAC.) Some old-time docs still call it MAI - no matter, the treatment is the same.
And sometimes it is referred to as NTM - Non-tubercular Mycobacteria because TB is also a mycobacteria as is leprosy.
Terminology can be a tricky world
Sue