I think mirroring is part of many human interactions, not just with Ts. I experienced it with both of my therapists, especially in communication style. With the first T the latter was very obvious as his default style of quite different from mine: I could see what may have been more his own natural style in the first couple sessions and also when it was disrupted towards the end when we had lots of conflicts.

Interesting about the leg crossing. My current T always sits with his legs crossed, I noticed this and wondered why, I would think it's perhaps a bit usual for men? But I do also almost always sit on the coach with my legs crossed so perhaps we are mirroring each-other? This wasn't the case with my previous T.

There is something else my current T does all the time with verbal communication. Often when I speak about something significant about myself and my life, he would respond telling me a similar thing about himself and his experiences. This is definitely a method that works to make connection with me not only because it creates a sense of similarities but also because it seems very natural. When former T tried to say things to connect with me, often it felt very contrived and off. I think that successful use of mirroring requires more than just mimicking body language and reflecting things back to the patient. Whatever it takes, it is not effective with just anyone.