Yeah, that is part of its deception at times. For the races which have full results posted you can look up the resulets and figure what spot a DNF is.
The other thing to be aware of is that if you look at drivers stats for some of the older races, only wins are figured into a drivers stats.
Still it has more complete records than any online site I know of right now. Decades of Racing has some good stuff, but again lists mostly winners only.