Yes, that is true. Custom in AKK belt promotions is touching your head to the new belt (transfering the knowledge into the new rank), and being hit at the end of the belt test (experiencing the pain of being "born" into your new rank).
This starts progressively with a fairly gentle heel palm to the abs on your first promotion. Which later becomes a full punch. By brown belt, you are expected to be able to receive a full power kick to the midsection.
Mr. Parker was known to kick all ranks, but his control was such that he would not hurt the beginners. But they did usually end up on the floor.
The custom at my particular AKK school was that ALL the black belts got to hit you.
I have video of my own BB test where my instructor kicked me, and I might upload it, if I can ever figure out how.