  The recent discoveries of the bottomonia states h_b(1P) and h_b(2P) confirm
the quark model prediction, already verified in the charmonia sector, that the
hyperfine splitting of P-wave mesons is very small. The striking agreement is
somewhat surprising because the non-relativistic result, for which the
splitting is zero, may be modified due to large mass shifts from coupling to
open flavour meson pairs. This paper is based on the observation that in most
models hyperfine splitting remains small despite what are in many cases large
mass shifts. This effect is shown to be a generic feature of models in which
the coupling is driven by the creation of a spin-one pair.
