I don’t think it’s unreasonable to think your spouse shouldn’t have an opposite gendered friend with whom they spend a lot of alone time. It’s not just about trusting your spouse, it’s also about trusting the friend. Couple friends and friends groups are great, not sure why my husband would need to spend a lot of time alone with another lady. There are plenty of women I trust him to be alone with, but they’re all also my friend, and usually their partner is a friend as well.
Last time my husband had a female friend who was not mutual she ended up sending pictures of herself drinking in the shower to him. She was also in a relationship at the time, so he thought she was just a platonic friend. I trust him, I don’t blindly trust people I don’t know.
How exactly do you think bisexual or pansexual people function? Do you think they just don’t have friends? If not, why is it different for heterosexual people? I genuinely don’t understand. I’m not trying to do a ‘gotcha’ or a win a silly internet argument or anything like that. I just genuinely have never understood it and I want to so I keep trying. My best guess so far is it’s just a mix of insecurities and weird gender norms and heteronormativity.