This is not to deny both Alex' and Chan Tran's experiences but I suppose the only way to reach a meaningful conclusion would be to get all the F5 and F100 users here on APUG and probably elsewhere to give their experience of underexposures to reach a statistically significant conclusion.
It just seems to me that if this was a feature of both cameras then an awful lot of users should be complaining in forums and complaining to Nikon and maybe affecting sales of both models. I have seen a number of threads on both cameras and I can't recall seeing many complaints of this nature.
On the issue of correcting the underexposure I'd have thought as Alex says that lowering film speed would correct the problem. If the problem can be rectified via a spot meter for instance or an incident meter in the right circumstances then isn't this in effect the equivalent of lowering the film speed i.e the F5 user overrides the matrix and the camera does what it is told and produces a correctly exposed neg.
It cannot do otherwise