It is entirely possible for runners to get round these sorts of races without navigation skills - you could do a MM with a partner who does all the navigation and the vast majority fellrunners get round most races without a recce, simply by following the runner in front.
I suspect far too many fellrunners have little to no navigational skills. After starting orienteering, I am now aware of how poor my navigational skills were. They are getting better through practise, but there is still along way to go...