I have used Kanuma for Picea. But Picea are not that fussy. Akadama has a pH that is only slightly higher. Spruce do fine in Akadama. The issue I see is Akadama looks "natural" as a soil media. Kanuma, is bright yellow. If you pot a spruce in Kanuma, you will have to cover the kanuma with moss before a show as the kanuma is just plain "ugly" for display purposes. With azalea, we always cover the kanuma with a layer of moss, so Kanuma is not an issue color wise.
Kanuma is less widely available in North America than akadama. Even akadama is hard to get. Most will use akadama as it is slightly easier to get and slightly cheaper too.
Spruce are not that fussy about soil. They will grow fine in akadama, they will grow fine in Kanuma, they will grow well in pumice they grow well in bark mixes. They grow well in a wide range of potting media. There is no need to worry about the slight advantage that kanuma may offer in terms of pH. It is not a "significant factor" or a "limiting factor" in growing spruce.