Peter, I think you're right when you say with "creamy" people mean subtle tonal gradation... And I guess that richness is enhanced by lack of grain (or larger formats, for the same reason...) but it requires very good exposition (not the so common underexposure visible in most B&W) and the right development too...
Many times, though, crisp -not dissolved- grain texture adds another kind of richness to surfaces and their tonal gradations... That's inherent to photography, and so peculiar... That's the look I like the most: grainy, but with clear, separated midtones, and punchy contrast, with pure black, and -if the scene contained it- pure beautiful whites clearly separated from high grays... As the tones found in the swimmers shot...
Cheers,
Juan