Question about IoBuildDeviceIoControlRequest

Hi all

I have a question about IoBuildDeviceIoControl Request . In DDK
documentation , it says

"IRPs created using IoBuildDeviceIoControlRequest must be completed by
calling IoCompleteRequest and not by merely deallocating the IRP with
IoFreeIrp. "

But when I checked the sample code in DDK , none of the samples either frees
the IRP or completes the IRP . T