Are we moomin, or are we dancer?
The European psychological associations study on sexual orientations are making this pansexuality thing took increasingly faddish.
Long story short, There are traceable differences between "strongly heterosexual" and "Strongly homosexual" and "Bisexual" in both neuro and emotional response to stimuli but none yet traceable between "Bisexual" and "Pansexual" Individuals, which means it may not be recognized as evidence is stacking up to basically state that "this shit is made up".
This does assume that emotional response is a valid proxy for sexuality. It might describe some, but there's no clear reason it should describe all possibilities. [I actually agree with you though]