As the husband of a Marriage and Family Therapist operating in NYC and upstate, I can tell you that most client notes are still done on paper, and locked away. My wife's notes are either locked in a "safe" at her office (heavy time-locked door to a room, with locking file cabinets) in the city, or in a small locking fire-proof file safe at home.
Really the only things that get computerized are the things required by insurance (diagnosis and treatment plans).
But notes are highly personal to the therapist, and can include any number of on-topic or off-topic , and it is rare even under subpoena to release your personal notes. Her office has a lawyer on retainer who's only job is to quash subpoenas. She's never had one served to her, and I dont know if any of the other clinicians have.
But back on topic - though, I'm 90% sure the clinicians at the psychotherapy clinic in GP's comment probably had the same thing. They would take paper notes, and only digitized what they needed to digitize, and most of those digitized records are non-transferable anyway, because they would be diagnosis and treatments for that patient/client provided by that clinic, and if a clinician left, and was allowed to take clients/patients to their new practice (sometimes allowed, but often times not), the clinician would take their personal notes with them.