I just wanted to add a couple of things. If this doesn't make sense or if it is unnecessarily complicating then just ignore it, however...

After a lot of controversy...

Some theorists are saying that it isn't necessarily that transference responses are inappropriate in the sense of being completely out of touch with present events that prompt (or trigger) them. This has arised largely in reaction to prior theorists who used to regard fairly much ALL of the clients responses as being transference based and as such they didn't look at their role in events. (Some theorists / clinicians still see things this way though fortunately it is changing now).

For example: Most people don't like to be kept waiting. Especially if the therapist is repeatedly late or keeps them waiting well into the scheduled hour. As such, some sort of annoyance / frustration / negative response would indeed be understandable given that the therapist is indeed late and given that nobody likes to be kept waiting.

That being said, sometimes the particular form of the feeling (e.g., hurt) and / or the intensity of the feeling (really very upset) can derive from the past. Even if the response is the typical response (of fairly typical intensity) of simply not being happy with being kept waiting it could still be profitable to treat it as a transference response, however, in the sense of talking about past hurts along similar lines. Since therapy is meant to be about the clients responses and reactions it could be profitable to explore this even if the therapist is making a habit of being late.

But to focus solely on the clients response and to label it 'transference' can sometimes be a way of a therapist refusing to look at their role in the events. If the client is upset because the therapist is habitually late then the therapist needs to sort out for themselves (and probably not share this with the client) why it is that they are habitually late and figure out a way to stop that happening.