Demisexuality is under the asexuality umbrella, so it should seem relatable.

If you do experience sexual attraction towards those you are close to then that would be demi. If you want to have sex despite lack of sexual attraction, then that would be black-stripe ace.

The food analogy is the comparison I've seen people use to explain what sexual attraction is. Hunger is like libido and has little to nothing to do with sexual attraction. Sexual attraction would be like when someone brings out a fresh cake and you need to have a piece even if you just ate and are not hungry. I guess demi in this analogy would mean you wouldn't feel that way unless you already knew that specific dessert well. But if you just eat tasty desserts when you are bored, because you like the taste but don't have the mouthwatering reaction to it being presented, because the person who made it is important to you and you feel eating it's a way to bond with them, etc, you could still be a black-stripe ace.

That said, what counts as sexual attraction has confused me a lot despite spending a fair bit of time reading people trying to explain it.

Anyways, if demi is a functionally useful label, there no need to change. In-practice real-world usefulness of language is more important than weirdos on the Internet trying to be precise in the meanings of words.