  The rapidity-odd directed flows ($v_{\rm 1}$) of identified hadrons are
expected to follow the coalescence sum rule when the created matter is
initially in parton degrees of freedom and then hadronizes through quark
coalescence. A recent study has considered the $v_{\rm 1}$ of produced hadrons
that do not contain $u$ or $d$ constituent quarks. It has constructed multiple
hadron sets with a small mass difference but given difference in electric
charge $\Delta q$ and strangeness $\Delta S$ between the two sides, where a
nonzero and increasing $\Delta v_{\rm 1}$ with $\Delta q$ has been proposed to
be a consequence of electromagnetic fields. In this study, we examine the
consequence of coalescence sum rule on the $\Delta v_{\rm
  1}$ of the hadron sets in the absence of electromagnetic fields. We find that
in general $\Delta v_{\rm 1} \neq 0$ for a hadron set with nonzero $\Delta q$
and/or $\Delta S$ due to potential $v_{\rm 1}$ differences between $\bar u$ and
$\bar d$ and between $s$ and $\bar s$ quarks. We further propose methods to
extract the coefficients for the $\Delta q$- and $\Delta S$-dependences of the
direct flow difference, where a nonzero constant term would indicate the
breaking of the coalescence sum rule. The extraction methods are then
demonstrated with transport model results.
