He wasn't really standing there with the boombox. She imagined or dreamed that. The sequence has a slightly ethereal air to it and is a representation of her inner struggle. He was already grieving her at that point and the onus was on her to get him back, which she ultimately did by showing up at the Karate place.
shareIt was an immersive experience a day it was so good to see it at the cinema.
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Nah, he was really standing there with the boombox
There was nothing about her character to suggest that she imagines anything that vivid and no prior inspiration that would lead her to conjure that precise image
The whole point of that scene is to show what Lloyd would do, not what Diane would imagine
Interesting theory though
The scene was filmed separately at a different location rather than actually outside her window.
I think that gives the scene a sense of him not being there because he wasn’t.