This has been a long-standing misconception based on a shoddy interpretation that's itself based how on one single line, one single term, was translated. It ignores all surrounding context in the short story and in the characters overall, but the fandom is just oh-so-good at taking sketchily translated lines and turning them into something ridiculous that changes the entire way that character is seen.
Of course, we're referring to A Beautiful Flower Blooming Violet Every Sixty Years. We're referring to the line "They must have come to watch the sinful violet cherry blossoms. You can't oppose them, so we'd better retreat, okay?", that was previously explicitly worded as "we're no match for them". We're acknowledging that Yukari, Yuyuko, and Reimu are there talking, and Eiki is approaching. Yukari says this line to Yuyuko, and they skedaddle. Magically, this now means that Eiki is the strongest motherfucker that exists because this must literally mean that even if all three of them ganged up on Eiki in a fight that Yukari somehow figured would happen if she showed up, they wouldn't be able to defeat her. Right?
It's really starting to frustrate me. There are so many levels of flubs that led up to this being a widespread concept, but I guess the fanbase just really likes it enough to stick with it, despite various efforts to fix it. That's why I wonder how this is still a thing.
I'll explain why everything is wrong in the morning or whatever.