I don't know how or where this rumor started, but it isn't true (yet). I see all the news aggregators are repeating it, though.
On the Visitor Center section they still refer to LGBTQ+. They can't even be evil competently.
Found the source: https://www.erininthemorning.com/p/after-trans-people-trump-now-erasing
They wrote that piece well and linked to archive.ph so people can see the history. They have a snapshop from July 10th with 'bisexual' erased, but as of July 11th, it is back. As I write, the text they cite reads:
Before the 1960s, almost everything about living authentically as a lesbian, a bisexual person or a gay man was illegal.
It still omits transgendered as it has since the Februrary 'purge'.