Suppose you have a simple 1D problem with a potential which is such to allow for bound, quasibound, and free states. Are the quasibound states orthogonal to the bound states, or is there some slight overlap?
Mathematically, only the bound states, which have square-integrable wave functions, are "states". The bound states span a subspace of the Hilbert space so, by definition, everything else is orthogonal to them.
"Quasibound states" are technically part of the continuum spectrum. (There are some potentials, which go to $0$ slowly at $\infty$, that have more complicated spectra.)