I appreciate your take on this and I wish we were talking more explicitly about this in LGBTQIA+ spaces. The theory of how bpd develops is complex and probably includes biological factors (think, brain differences leading to sensory issues, memory issues, etc which then lead to certain experiences being more challenging to recover from) but you are correct that the experience of trauma and invalidation in childhood are central to the development of bpd. If we have a society that uniquely traumatizes trans folks, it makes sense that more trans folks than cis folks would have bpd as a result.
One of the more disturbing facets of some of the new anti-trans legislation in US states has been language that seeks to make it impossible for someone autistic or someone who has a personality disorder to access gender affirming care.
This ableist language is clearly the next line of attack and serves to dehumanize not just trans folks but also folks with personality disorders and neurodivergences. Anyone who thinks that these governments intend to stop at murdering trans folks is a damn fool - these laws make it clear there are other groups they intend to target.
Your point is precisely why I voted against this law. Tried to argue it with some of my local friends but don't think I changed any minds (unfortunately).