We naturally play different roles at different times in our lives. Sometimes we are unaware of these roles because they are so much a part of our everyday lives. Effective interviewing requires a particular role, as does working in your profession, being a parent, friend, spouse, dating, or playing in your favorite sport. Everyone plays various roles at different times, often in the same day; we just don't give it much thought.
Playing different roles under varying circumstances does not mean we're inauthentic — it simply means we are acting appropriately in the situation.
A job interview isn't something we do every day, therefore we typically have not developed an effective role for interviewing. Skilled interviewers, on the other hand, have developed techniques for being effective in their role. You're not going to win a baseball game if you don't know the rules and develop an effective role as a player!
Landing the job you want means developing this effective interviewing role, otherwise you will likely bring other roles into play — without being aware of it — that will not be appropriate for an interview.
Being successful in any new role takes some thought and preparation. The small amount of time and effort you invest can pay significant returns in income, quality of life and satisfaction.