I agree and also believe:

Whoever takes the most risk in criticizing the other....
Whoever is identified as having the problems....
Whoever is expected to accept criticism....
Whoever has the expected obligation of "growth"....
Whoever is "labeled" with illness and disorder....
Whoever is identified as outside of the norm....
Whoever is identified as dependent, needing a strong other for decisions or function....
Whoever is instructed, given rules, restrictions and boundaries....
Whoever is most seeking the other's caring, approval and praise....
....has the least power

Whoever is identified with authority and "expertise".....
Whoever is the most detached, taking the role of the "observer"....
Whoever has the most permission to judge, evaluate and disapprove....
Whoever controls the narrative and interpretation....
Whoever diagnoses and labels the other....
Whoever can condescend, goad, bully or belittle with the least consequence....
Whoever sets the stage and the rules....
Whoever is the least flexible and available....
Whoever withholds his own self-doubts, deficiencies and weaknesses....
Whoever can (unapologetically) chose not to speak or respond....
Whoever puts forth a protocol without explanation, rational or disclosure....
Whoever can break rules and promises, or change them, with the least consequence...
....has the most power

And, frankly when we consider therapy a contract between two equal human beings, these roles can be unearned and arbitrary....