Adafruit RTC begin() not returning false
If you look at the library source code it will be clear why begin() returns true.

From https://github.com/adafruit/RTClib/blob/1.2.0/RTClib.cpp#L434-L437:

boolean RTC_DS3231::begin(void) {
  Wire.begin();
  return true;
}


I suppose they plan to eventually make the return value of begin() mean something but for now it does not.