CXPACKET SUSPENDED and NULL wait type

I was was running the query in this article:

http://ift.tt/1D22xjz

To see what my threads were waiting on in regards to a suspended query with a wait type of CXPACKET.

However for the SPID in question threads that are running were showing wait types of NULL with every other thread in a SUSPENDED state with a wait type of CXPACKET.

I was expecting to one of the threads having some kind of wait type other than CXPACKET, can anyone explain to me what is happening in this situation?

Thanks