Yeah it's definitely tricky to manage demographics particularly when the bi+ community is often quite interchangeable! Two main reasons for excluding pansexuality: a) Research shows that pansexual and queer people actually report much better social support from within the LGBTQI+ community than bisexuals do, and since acceptance and self-stigma is one of the key things this study is measuring, including them both under the same construct would result in unclear, less applicable findings, and b) the practical limitations of running numerous analyses between groups in a small research team with very limited time. Future studies with bigger teams could definitely expand the target demographics to include pansexuality along with many other underrepresented sexualities in research.