I believe what you're saying is true about many JWs, they haven't logically concluded ANYTHING and so made the decision to be a JW.
I think that the WTS dogma is designed to appeal to certain emotions and fears that most people naturally have, fear for one's children-their health and future, our spouses, our own lives. It's just sales! A need is pointed out then the solution is then sold.
You make a good point about your friend. How easy it is to close your eyes and click your heels together and say 'there's no place like the new system there's no place like the new system' when you worry about these most dear things.
They call it 'throwing one's burden on you-know-who'. I call it refocusing worry in a positive direction.