I would argue that sexual attraction to a non-op trans woman involves attraction to male genitalia, which by definition and logic extend beyond the label “straight”. A different case would be a man attracted to masculine presenting women (tomboys), or post-op trans women, which would not rule out bisexuality, but be within the defining bounds of straightness.

Because the visual overlap between non-op trans women and femboys is quite noteworthy, an umbrella term for attraction to both male and female identities such as “bisexual” is appropriate. Denying that is arguably Bi-erasure! I hope you understand my point.