For the same (effective) CI the silver density is about 2/3 that of a non-pyro neg developed to the same CI; the remaining 1/3 density is stain. Or iow, as far as light transmission's concerned the density is the same.(posted 8555 days ago)Or to say it differently, it's as if you developed the film less and then added a proportional stain, giving the same overall density.
I think the term "block" is misused; traditionally it means that additional exposure doesn't result in increased density, or the curve slope is flat, no contrast. I believe what Hutchings is referring to is negs that simply have a far greater density range than can be printed.
When printed on VC paper, the color of the stain acts as a lower-contrast filter proportionally to density, so that the higher the density the lower the printing contrast; this dramatically compresses the lighter tones.
The same degree of compression of the high end can be obtained with extremely-compensating development.
Note that reducing contrast, whether via stain and VC paper or compensating development, on a practical level reduces the slope of the curve and at some point _will_ block, or there won't be enough contrast to make a printable detail.
To me, this usally makes prints that have light tones that look like flat grey muck and imho is only useful when there's an extreme brightness range in the light tones in the scene.