the answer is no, there were never any "true christians" there never have been any, theres not single group or denomination in the history of christianity who were "true christians"
even the first followers of christ never agreed on anything even whether christ was devine or the son of god, as for the NTS thing, it comes down to people pointing thier fingers at someone who doesn't agree with them and saying "they arn't true christians!" in reality they are saying "they aren't true christians, because they don't follow my churchs dogma!"
if people want to argue that the disciples were "true christians" they never agreed on anything eather infact the scizm between paul and peter shows there never was a "true christian" church
so the whole true christian thing is nothing but a dismissel of someones beliefs you don't like