This is not a correct description - there may be cases where annotations (I assume that you mean use of "tailf:xxx" extensions - the attributes requested by get_attrs() are not modeled in YANG) affect whether get_attrs() is actually invoked, but the requirement for its implementation is stated in the confd_lib_dp(3) manual page:
This callback only needs to be implemented for callpoints specified
for configuration data, and only if attributes are enabled in the
ConfD configuration (/confdConfig/enableAttributes set to true).
Thus in the specified case you need to implement it, in other cases you do not - and in all cases regardless of annotations.