On A Recent Claim Concerning $\tau (D_s)/\tau (D^0)$

It has been suggested that the observed $D_s - D^0$ lifetime difference can be `understood' as due to $SU(3)_{Fl}$ breaking in the phase spaces for the exclusive $D^0$ and $D_s$ channels `removing' the need for weak annihilation. It is pointed out that several of the statements in this argument are misleading or even inconsistent with a state-of-the-art description of heavy flavour decays based on the operator product expansion.