In humans,
rods are predominately located in the periphery of the retina, which are areas of reduced resolution (this would be like areas of peripheral vision. The fovea (central point of the retina which is normally directed to points of interest) has both the highest concentration of photoreceptors and the most cones.
If the cones are replaced by rods then the rods may be able to make up some of the lost resolution
@Chatul discussed (different diseases causes could do this differently), if not their retinal distribution might help explain those results.
When one goes from a highly illuminated environment to a dimly lit one, it takes several minutes for the rod cells to adapt to the darker levels of illumination. Until that happens, the rods are not that effective at sensing light. This is well know to those who have to have good night vision (for example those who are watch on ships at night).
In addition, rod photoreceptor molecules, rodopsin are located in disks of the outer segment (see wikipedia picture). The disks have a lifespan and are periodically shed and replaced. This happens more quickly at higher levels of illumination and could affect you scenario.
While rod photoreceptors are much omre sensitive to low light levels, an apparent tradeoff is that they are slower to produce a neural signal in response to light. This would also affect the no cone scenario.
It appears that there are also circumstances where
high illumination can kill rod cells.