This is coming as a kind of slow realization to me (like a lot of other stuff) - that I would not even know the JW organization of today from what I remember in the 1970s.
In those days, not one witness would ever take seriously the idea that a 9-year old could or should be baptized. 16 was considered very young...not until 21 or more was it considered that a young person was holding back.
The idea was that you took the commitment of baptism seriously on your own...and remember, they did not have to "join" anything, or sign a contract either. You were specifically told you were not joining any church back in those days.
But, prior to 1975, they were not all that desperate for numbers and growth - as they now appear to be.