Electroweak interactions assign a central role to the gauge group $SU(2)_L
\times U(1)_Y$, which is either realized linearly (SMEFT) or nonlinearly (e.g.,
HEFT) in the effective theory obtained when new physics above the electroweak
scale is integrated out. Although the discovery of the Higgs boson has made
SMEFT the default assumption, nonlinear realization remains possible. The two
can be distinguished through their predictions for the size of certain
low-energy dimension-6 four-fermion operators: for these, HEFT predicts $O(1)$
couplings, while in SMEFT they are suppressed by a factor $v^2/\Lambda_{\rm
NP}^2$, where $v$ is the Higgs vev. One such operator, $O_V^{LR} \equiv ({\bar
\tau} \gamma^\mu P_L \nu )\, ( {\bar c} \gamma_\mu P_R b )$, contributes to $b
\to c \,\tau^- {\bar\nu}$. We show that present constraints permit its
non-SMEFT coefficient to have a HEFTy size. We also note that the angular
distribution in ${\bar B} \to D^* (\to D \pi') \, \tau^{-} (\to \pi^- \nu_\tau)
{\bar\nu}_\tau$ contains enough information to extract the coefficients of all
new-physics operators. Future measurements of this angular distribution can
therefore tell us if non-SMEFT new physics is really necessary.