  In the vicinity of a narrow Feshbach resonances Efimov features are expected
to be characterized by the resonance's properties rather than the van der Waals
length of the interatomic potential. Although this theoretical prediction is
well-established by now, it still lacks experimental confirmation. Here, we
apply our recently developed three-channel model [Yudkin and Khaykovich, Phys.
Rev. A 103, 063303 (2021)] to the experimental result obtained in a
mass-imbalanced $^6$Li-$^{133}$Cs mixture in the vicinity of the narrowest
resonance explored to date [Johansen at. al. Nat. Phys. 13, 731 (2017)]. We
confirm that the observed position of the Efimov resonance is dictated mainly
by the resonance physics while the influence of the van der Waals tail of the
interatomic potential is minor. We show that the resonance position is strongly
influenced by the presence of another Feshbach resonance which significantly
alters the effective background scattering length at the narrow resonance
position.
