Its better to be honest and say you dont believe then to pretend.
A lot of missionaries kids are like that. They might have grown up in christian schools, might have put their hand up to say I accept Jesus into my heart. But if they didnt make any move to repent and make a commitment get water baptised, they havent really been converted.
Also they might believe they are a good person, but ive met a lot of people like that who are snobby about that and think they are just better than anyone else.
Believing means...you believe that Jesus Christ is the son of God, that he died on the cross for our sins and was raised to life on the third day...so we can have eternal life.
Whats missing from the fake christians life is the Holy spirit. One absolutely has to have the holy spirit. If or when they make that leap of faith, they will receive the gift of salvation...which is the holy spirit. And they will bear the fruits of the spirit.
I dont doubt that many receive the word, but the state of their hearts means it just isnt prepared to let it grow. It is with our hearts we believe...