Absolutely, the show should have been stopped while the injured member was attended to. While not DCI, there is a precedent (2005 Kilties -- DCA prelims). RIP Lothar.
Yes, the demands in DCI shows vs DCA are different. Seriously, the only downside I see to stopping a show is that a corps which was having a bad run could theoretically feign an injury so as to get a fresh start. Not saying anyone would but they could.
Hoping for a full recovery for that PC member.