It just occurred to me that between Reimu Hakurei's general level of skill and her antipathy for fighting youkai, she probably doesn't view defeating Extra-bosses as particularly significant, or at least the ones that aren't plot-relevant. Like the player is all "YES I cleared the Extra stage!", but in-universe I don't think she cares that much about it.
Like in WBaWC, after she beats Saki, her "oh, I beat Prince Shotoku's horse in Hell" has the same "narrative weight" in her mind as "oh, I beat a ghost baby" after she fought Eika. Her impression of beating Momoyo in Unconnected Marketeers is "Thank gods she didn't trying to sell me something and I got her card for free." Like if it isn't something like Actual Yukari Yakumo, or a plot-conclusion like Okina 2, Reimu just doesn't care.
