I do have somewhat of a theory - only tested a few times tho.
When I talk to a JW and ask or comment on a "touchy" subject, it SEEMS to me: if they have no doubts or (reservations) or lack of confidence in their "org/god", they will engage in conversation. If they themselves are dealing with doubt, maybe this subject had been brought up previously at another place & time and its been weighing on their mind who knows but they sure hi-tail it out of there.
I tend to agree. The cognitive dissonance probably makes the conversation too uncomfortable.