  $SU(2)_L$-invariance links charged dilepton $\bar
q\,q^\prime\,\ell^+\,\ell^-$ and dineutrino $\bar q\, q^\prime\, \bar\nu\,\nu$
couplings. This connection can be established using the Standard Model
Effective Field Theory framework, and allows to perform complementary
experimental tests of lepton universality and charged lepton flavor
conservation with flavor-summed dineutrino observables. We present its
phenomenological implications for the branching ratios of rare charm decays
$c\to u\,\nu\,\bar\nu$ and rare $B$ decays $b\to s\,\bar\nu\,\nu$ decays.
