  In this note, we discuss the effect of light, non-gauge, bosonic degrees of
freedom on the exterior spacetime of an exotic compact object. We show that
such fields generically introduce large deviations from black hole spacetimes
of General Relativity near and outside the surfaces of ultra-compact exotic
objects unless one assumes they totally decouple from the standard model or new
heavy fields. Hence, using black hole spacetimes of General Relativity to model
ultra-compact exotic objects and their perturbations relies implicitly on this
assumption or on the absence of such fields.
