That seems insane to me. There are plenty of bisexual individuals that children will encounter in the real-world no. I could sympathize with banning of books that are of a certain obscenity but if purely because they are bisexual that sounds unhinged
That was the underlying motivation of a lot of these book bans and why they were so open ended. The idaho law explicitly calls out "homosexuality" as a reason for removing a book.
Bigots want there to be no visible LGBT people in society. "Your child will encounter a gay person someday" is not an argument they care about because they would also like to ensure that gay people cannot be visible in other parts of society.