The alarm 10 min before the end of the session would bother me as well. None of my Ts had it set up, and, frankly, I don't see the need for it. The clock should be right in front of them, and so ending session on time shouldn't be a problem.

But the core issue is not whether the T is 5 min late or whether they have an alarm set. The core issue is that our inner process can't be squeezed into the schedule. Our psychological material comes out when it wants to come out and not according to the schedule. That's why the whole traditional therapy structure where you have to pour your thoughts and feelings out only within the specific window of time and at the time specifically scheduled for this is not helpful IMO. Therapy should be designed in such way that it would follow your pace rather than force you to produce emotional material by the schedule. People should have the freedom to schedule appointments whenever they want. It doesn't have to be a regular thing. The session time also should be flexible. If I remembered something important by the end of the session, I should be able to have some reasonalble extra time to process it instead of just being forced out the door.

But for that to happen, we need the universal health care system where therapists wouldn't have to count every minute of session because they have to charge you for their time. Then both therapists and clients would relax about the time because the therapist would be getting their paycheck from the government and wouldn't need to stress out about every single minute that goes unpaid. In the capitalist economic system where therapists have to charge for services this won't happen. I talked to someone who worked as a psychologist in Israel and she said that no one cares about starting and ending sessions on time there. Over there the time of the appointment is more like a suggested point of reference rather than the exact time you have to show up. That's why the therapist doesn't make it a big deal when the client is 30 min late because, most likely, he or she is still in session with someone else at this point. Vice verse, the client is not bothered if the therapist becomes available 20-30 min after the appointment time. It's just part of the culture where people are very relaxed about time and don't give it much of a significance.