Seiryū stone was name inspired by azure dragon. It has a blue tint to it, and came from outside of kyoto. The area of harvest is now a park, therefore harvest, and export are illegal. Most of what you see now under the label of Seiryū is not blue tinted, and imported from china to japan, then exported out. How much blue tinted stone do you see out there? Not much from what i see.
By doing so it is legal to label it as Seiryū stone. Like olive oil imported from italy (as an example), it's actually from greece, but packaged, and labeled in italy which allows it to say from italy.
Seiryū stone is now loosely used terminology for similar characteristic rock which allows sellers to keep the price high, and maintain it's mystique.
That's my issue with the labeling of rock.
If you go to japan, and go to a store, and buy rock, it's illegal to bring it back with you. It's considered "organics" , and falls under customs laws of japan.
I'm not into the image, but into the hobby...