Well, Loki's a bit more than just bi. He likes animals too, horses for example.

Maybe he's just dumb and/or lacks awareness

Not gonna lie, I thought Loki was pan.

alright and what's the issue? since he's your boyfriend he likes you so he obviously isn't trying to hurt you. so instead of being insulted by his "mansplaning" who not teach him? being conditional especially with people close to you isn't doing you or your community any good. for the record, Loki can change his gender and species at will and it's rarely depicted in the form he was born so good luck labeling him.

first what's your definition of mansplaining (it isn't just a man explaining something) my sister has used this term before because a male "told her information instead of suggesting it" even though he was correct and she did not know the meaning prior. is he a big comic or MCU nerd and maybe you are not? if so he could have been excited to share his knowledge of the character, and not explaining what BI means... sometimes people are just trying to share the things they love, even if they share with someone who already knows. either way, maybe talk to him about your feelings before being judgy. probably didn't mean anything by it.