?? I don't get this. Why couldn't she see a first-time client, a client who goes on a more flexible schedule, or an emergency appointment during this time? When I'm away, I don't expect my T to sit there during my appointment, holding my spot and not getting paid. I'm sure he fills it with another client.

Based on who I've seen when I've been going in/out of my sessions, T has some people he sees at a regular time each week, and some people with more flexibility. It doesn't have to be either/or.