Please refresh my memory on HIP_SIGNATURE in UPDATE

Robert Moskowitz <[email protected]> Sun, 18 Sep 2016 19:19:40 +0100
Newsgroups gmane.ietf.hipsec,gmane.ietf.hip
Message-ID <[email protected]>
I cannot remember why we mandated HIP_SIGNATURE in UPDATE packet, 
particularly when we have the HIP_MAC.  Sec 5.3.5 in 7401.

I am sure we had a good reason, but I am not finding it....

thanks

Bob