I am studying hadronic decay of the $W^-$ boson. I am aware that the decay into quarks from different generations is not possible and that charge as well as the total angular momentum have to be conserved. Why are we only considering the decay into two particles? For each decay that is possible, we could simply add a quark and its antiquark (or multiple of these pairs as long as the mass does not exceed the W boson mass) without changing the total charge and also the spin-projection onto the z axis of the two additional particles can cancel out.
What is the reason that this is still not possible?
My only guess is that it has something to do with addition of angular momentum. Is it not enough that the $z$-projection of the total spin remains conserved but does the square of the angular momentum operator (for the irreducible representation of the total angular momentum) also need to stay the same? Does that mean that the spin quantum numbers of the new particles always have to add up to exactly the spin of the initial particle?