STOR remembers a ton of properties of the particles it eats, it uses every available property to store this information. For example, the ctype of the eaten particle gets stored in a rarely used variable called pavg1.

There isn't really any place to store this extra info. If there was any available space for this, we would already be using it to store more properties of the eaten particle. So you can only filter on .type, not on anything more specific.