That is the law, I think. Anything that is not a seed...sticks, straw, dirt, mulch, water absorptive coating and so forth must be listed as "inert". Seeds--even if they are not viable are not considered inert matter. Sod growers buy seed on the "PLS Basis" pure live seed; they subtract out the non-germinating seed. (And then compare costs.) The label cannot mention the word fertilizer. Now if it claims to be a fertilizer--fertilizer laws apply. The fertilizer analysis must appear on the front.