Most of the replies here aren't giving you a solid answer, though @finitebanjo@lemmy.world was close—so sorry about that.
At one point, the bill text included anti-refugee, anti-CRT, and other controversial provisions that Republicans added, but those were fortunately removed.
However, the anti-trans language was reportedly "slipped in" and didn’t even appear in the bill summary. The bill itself has been described as "must pass," which means it’s prioritized regardless of what’s in it.
Final takeaway: Bad actors in Congress added the language, and Biden didn’t care enough about trans rights to thoroughly review it.
Sources:
didn’t say it was. it was an intentional manipulation of the law, as i wrote above.