Do people seriously conciously fantasize about taking part in erotic acts with real people (especially ones they have feelings for)?
Yes.
I kinda get the disrespect perspective, maybe. I felt that a little as a teen. But then I thought it probably wasn't respectful treating my crush in my mind like a sort of sexless statue or object rather than a real human being that I was in love with and wanted to have sex with.
It doesn't make me want to necessarily sleep with them either, but rather stay up late having sex with them. And maybe after sleep.
But this idea of asexual romantic attraction makes about as much sense to me as saying "When I am hungry it doesn't make me want to eat food."
When I say I have "romantic feelings" for someone, the feeling I'm referring to is a combination of love and sexual desire. Even when I was a kid and would sort of push down or repress sexual thoughts because in my head it felt wrong or inappropriate, what I was feeling was sexual desire and love.
My understanding of the term "romantic" has always been euphemistic, based in an understanding that it would be weird and rude to just tell someone you're crushing on that you love them and you want them to love you too and you want to put your mouth on their genitals because you think you could make them feel really good and you want to physically intimate to be vulnerable with them because vulnerability is a part of of not just physical but emotional intimacy and you want them to share their feelings and feel open to you and so on and so on you get the idea.