A few years ago I wanted to find out more about the Suzuki method. There was a Suzuki teacher at the conservatory where my lessons are held. She was in her 60s, probably retired by now. Attended a 1 day workshop hosted by 3 Suzuki teachers who taught piano, cello & violin. Got many questions answered.
The first thing that came up for discussion was the "native tongue" method. S Suzuki came to the conclusion that kids learn their native language naturally at a young age. They are encouranged to start music lessons as soon as they can walk at 3 or before 10. Suzuki went to Germany to study music in his 20s but had trouble mastering the German language. The comparison to learning a language was based on S Suzuki's life experience. Kids learn languages or music faster than adults is a myth. There is no scientific proof this this the case. I know someone who studied Japanese and tried to learn accordion as an adult. He didn't get beyond a beginner / lower intermediate level in either. Many Asians learn new concepts by rote than association.
There are 2 popular music methods out of Japan: Suzuki & Yamaha mainly for kids. Both require parental involvement in the learning process. A parent of a kid in Suzuki are expected to learn together, take notes in class in order to act as a mentor at home. A parent of a kid in Yamaha is mainly for emotional support. Does parental involvement work? I met young people who were in Suzuki or Yamaha. In 1 family the kids learned music to a high level and performed at their grandfather's funeral. In another family mom said she practiced piano more than her son and his first recital was an embarrassment. The kid quit after a year. As good as a learning method can be, dropout is not inevitable depending on the student's interest in music and the circumstance such as other commitments.
A Suzuki parent who accompanies a kid to a lesson would learn as much. So far I have yet to see a parent who considers himself /herself an amateur musician. The focus is on the kid being the "talented" musician. Maybe some parents would get into serious playing themselves but the Suzuki parents I talked to only learn piano to act as a mentor at home.
Is Suzuki suitable for adults? After an online search the answer is yes but... Suzuki teachers are trained to work with young kids so not all teachers are willing to take on adults. Suzuki Book 1 has songs intended for kids like "Mary Had a Little Lamb", "London Bridge is Falling Down", etc. You'd be better off learning songs out of Alfred's or Faber Adult Piano.
Suzuki Books contain pieces in the order of difficulty. This is supposed to be a structured way of learning. Well organized but rigit. Once I asked a Suzuki teacher a question regarding fingerings of a beginner piece. Something like this E has finger 3 on it, another E further down also has 3 on it. Based on the finger sequence, would be easier to play the next E with a different finger. The teacher's response was "Book 1 used to have the old fingerings as you suggested but the Suzuki Association decided it's less confusing for a kid if both E use the same fingering". IMO students shouldn't associate a specific note with a fingering depending on what comes before & after.
Other findings: some Suzuki teachers use only Suzuki Books and teach the songs from each book in order. Other teachers are ok with students learning pieces not in a Suzuki Book. A Suzuki lesson always starts with a bow between the teacher & student which is a common Japanese greeting. This is not just a friendly gesture but reinforces the idea of respect for the teacher. A Suzuki teacher is a trained professional and therefore students should not dispute anything being taught. In my part of the world, the Suzuki Association of the Americas publishes a monthly magazine featuring success stories from teachers & students using the Suzuki method. S Suzuki is often presented in articles as a great man with a kind heart. Suxuki insiders often elevate S Suzuki to something like a holy man. Sayings by S Suzuki that have nothing to do with teaching / learning music are included in articles.
If CBS 60 Minutes is going to do a documentary on the Suzuki method, they would need to include Suzuki's biggest critic Mark O'Connor who called Suzuki a "fraud". Suzuki Associations around the world have an answer for every critism and defended the reputation of Suzuki.
1 of the most debated event was the 1961 meeting between S Suzuki and the famous Spanish cellist Pablo Casals in Tokyo. There was a welcoming concert organized by The Talent Education Research Institute for the cellist and his wife when they visited Japan. 400 Suzuki students who perforced various pieces during the concert. Suzuki insiders claimed the cellist was moved to tears after hearing the concert. Critics including O'Connor argue that Casals was there to see his former pupil Yoshio Sato and his students perform, not an endorsement of the Suzuki method. Certainly good marketing for Suzuki.