>>49659743
Sanae is for sure a cheerful and :D character, but that's only part of her. When I say it captures her essence, I mean that it captures the other part of her that's only ever briefly touched on in MoF, where in her omake it says that she was scared to go to Gensokyo, where she thinks that the people are primitive when she arrives. I feel like these images capture that feeling of dread or feeling lost, she's made to be a small, perceiving part of the image hopelessly tiny and overpowered by the wild landscape around her. It all ties back to her stage theme, as you said, "The Primal Scene of Japan the girl saw" (or watched, if that's the translation you prefer), just her, alone, perceiving this land that's completely alien to her, all the while feeling unsure and scared. Later on, that gives way to her completely assimilating and feeling at home in Gensokyo.
So while it may not capture the essence of Sanae as we see her now, it captures the essence of how she was in the past, way back in MoF.