I agree that there’s something to be said for examining your characters through sexual, romantic, and other intimate encounters with each other. It’s totally fair (and even to be expected) that some of those results would end with the revelation that a character IS asexual for example, and struggling with the fear of rejection from someone they expect to have an active sex drive. A scene like that says a lot about the characters involved, and it’s such a relatable fear.
There are all these layers and different kinds of intimacy. and I feel like that’s really the magic gold that you’re getting at when you ship a pair of characters: you figure out what wavelength, what texture their intimacy is, and that tells you so much about them; it reveals familiar hooks that people can use to relate to these characters.