In this case I believe there is a very good chance that the ABC negative used for the test had about optimal printing density for both AZO #2 and a #2 VC paper. AZO is a graded silver paper that requires a negative with a DR of around 1.5. A regular silver #2 grade paper would need a DR of about 1.05 to print normally, but in order to print with the same contrast on a VC paper with a stained negative you would need to use a higher grade filter, or develop the negative longer for more contrast. Assuming the ABC negative was developed to an optimal density range for AZO the resulting density is probably very close to what you would need to match the contrast on a #2 VC paper.
Originally Posted by bmac
For further understanding of this issue see Frank's message today on printing VC and graded papers with a staining developer. The difference of about two printing grades that he observed with Pyrocat-HD would probably be even greater with one of the pyrogallol based developers than with Pyrocat.