The softer coticules will raise a slurry just with honing. For initial honing work, this is a great thing, but for polishing it is not because the hone is constantly releasing more cutting material and effectively acting like a lower grit, non-polishing, hone. It sounds like your vintage hone is in this softer category and is therefore not likely to be a good polisher. A good polisher is harder and is not prone to release slurry when honing with water.