Why there is no "cudaDeviceSynchronize" after cufftExecC2C's call?

[zhuwanggg]

CUFFT_CALL(cufftExecC2C(plan, d_data, d_data, CUFFT_INVERSE));

CUDA_RT_CALL(cudaMemcpyAsync(data.data(), d_data, sizeof(data_type) * data.size(),
                                 cudaMemcpyDeviceToHost, stream));

CUDA_RT_CALL(cudaStreamSynchronize(stream));

But in [https://docs.nvidia.com/cuda/cufft/](cuFFT API Reference)，we can get a sample with cudaDeviceSynchronize just behind the call of "cufftExecC2C".