Bisexuals have 2 soulmates if those who believe in soulmates extend the idea to it's inclusive conclusion across sexual orientation.
If the idea that men & women can't be friends is extended to its conclusion then that means...
☆ ☆ bisexuals can't have any friends ☆ ☆
Of course, bisexual individuals DO have friends. Moreover, LG individuals have mostly sex-of-attraction friends (or same-sex friends). It's only heterosexuals who have an issue with sex-of-attraction friends.
For instance, you never hear lesbians ask: Can women & women be friends?
As a sidenote, most of my friends are women. Of course having lesbian, asexual, & bisexual friends is logistically easier than having heterosexual female friends, but in most instances it's been just fine with straight female friends too (they're the majority).
Here's a study PrePrint my lab conducted on this topic (https://psyarxiv.com/x9u4p/), comparing sex-of-attraction friendships across sexual orientation