I was thinking that was the case, might have read it somewhere.Apparently it isn't water soluble in the zeolite, but the plants can access it. At least that was what I found with a quick tour of the first google results.
I wonder if it's too 'hot' to side dress plants with?
Might not be a good idea on food plants tho.
In any case, I think it's more beneficial in compost than detrimental.
There's not too much of it when I sift the poops out of it.