  Recently a two-step process has been proposed for the double-pionic fusion to
deuterium $pn (I=0) \to d\pi^+\pi^-$. Its calculation is solely based on total
cross section data for the two sequential single-pion production steps $pn
(I=0)\to pp\pi^-$ followed by $pp \to d\pi^+$. Though this sequential process
was aimed to explain the dibaryon resonance $d^*(2380)$ peak in double-pionic
fusion, we demonstrate that this is not the case. It rather fits to a possible
broad bump at 2.31 GeV in the energy dependence of the $pn \to d\pi^0\pi^0$
reaction, which was recently interpreted as a consequence of dibaryonic
excitations in isoscalar single-pion production.
