I don't think it's related to top/bottom but just simply "the way I get down" as an innuendo for "the way I get turned on". In other words, he's saying he wants to drive her because he finds that appealing as part of how he flirts. My $0.02.

Completely agree that the final montage sequence was weirdly clumsy and heavy-handed. I feel like it follows a Hollywood trend of assuming the audience is entirely clueless and will never figure out how things connect and relate, so everything must be highlighted and pointed out in excruciating detail. Not a fan, personally.