A new video on Youtube posted by NI appears to show something I thought was NOT supported. That is, my understanding was that the din output to external synths was only active if the S88 was un-plugged from the host computer. Unfortunately this forum will not allow me to post a link. Very helpful - not.
I'll buy an S88 tomorrow if I can have a zone or two of Kontakt instruments and control external synths without physically disconnecting the USB-C.