John Young replied to this question on another forum. And to be honest he does make a good suggestion.
A question first, who is to say that Colour Sergeant Frederick Wolfe and his 20 men were forward of the firing line? H.G. Mainwaring's sketch map of November 1879, has the bodies roughly in the same area as Captain Anstey of the Royal Engineers has placed the firing line at 1pm, or so it would appear to my untrained eye.
It is just my suggestion, and I've made it before on the forum, as to why battle debris was discovered during the battlefield survey in advance of the position that previously considered to be the firing line - skirmishers! Who in 2003 can say with an authority that skirmishers were not deployed at Isandlwana? No-one I contend. It may well be that Wolfe was in command of a party of skirmishers, who knows? Just my suggestion.