Yeah but it seems like the manga took some liberties to make the scene a little more dramatic. Definitely don't remember anything in the web novel about Sendai grabbing Miyagi's tie like that. It also seemed in the novel that Sendai was laying flat on her back when she got everything poured on her. Still, a nice different interpretation of the scene
I think these kinds of differences are as much about translation from written to visual media as anything else - in written media we can see inside the characters' heads and get a sense of how they feel, in a visual medium, conveying the intensity of feelings behind actions requires something you can actually
see; taking a few "liberties" here and there might be necessary to avoid losing out on important parts of the story.
An interesting contrast is with the adaptation of Uraseki Picnic - the manga is following the books
astonishingly closely, and somehow managing to capture the feel of the horror from the original, without losing anything by hewing so close to the written version. That's possible because the focus of the text is
outside the characters (despite being written in a first person perspective) - the horror is external, the things that are happening are external even though they're conveyed textually via a description of what the character experiences, and the emotional state of the narrator is a way of reflecting that external horror. The exception is where human relationships are involved, but there it's helped by the distance the narrator keeps others at - in many ways, human relationships are just another kind of external horror, and where they impact on the narrator the same kind of approach to capturing them visually can be taken.
ShuuKura is a very different kind of text - even when things are actually happening, the text focuses almost exclusively on the inside of the characters' heads, and the thoughts and feelings of the narrator for each chapter are the only source of information we ever get about those actions. The fact that it becomes obvous pretty early on that both sides are unreliable (in fact, often quite biased) narrators makes that even more important - grumpy Sendai gives us a different experience as readers from happy Sendai; grumpy Miyagi is . . . . . well, what we get almost all the time, but with different flavours . . .
This is one of the reasons I was skeptical about this adaptation - it's almost the worst possible case for a manga adaptation as far as difficulty goes. I think it's doing a pretty good job, though, using subtle shifts in the style of the art and presentation of the pages to convey aspects of the text that would be difficult to capture otherwise (particularly without a degree of exaggeration that just doesn't fit this story). And ironically, the relative dearth of action in the original text gives the mangaka quite a lot of leeway with the "liberties" they can take without causing meaningful shifts in the story.