No but it has a bearing on it. If a trans woman is a woman that was born in a male body, and said trans woman finds herself falling for another woman (trans or otherwise), then surely she is a lesbian, as opposed to if she identified with her body which would make for a heterosexual relationship.

Or maybe we just throw out the whole idea of orientation altogether, (a) because stuff like the above is just too confusing, especially when extrapolated from this simple case into more complex identities and attractions, and (b) nobody cares anyway now that all orientations are considered equal.