They're starting the Cotton Drifting Arc (Watanagashi-hen), but changed a major plot point into an incident from Massacre Arc (Minagoroshi-hen), this is very weird
Originally, Mion bitching to Shion about how Keiichi doesn't see her as a woman was the catalyst for this fragment's troubles, triggering Shion's PTSD about Satoshi. I wonder what'll happen now? I wonder if Mion overly gushing about Keiichi to her will have the similar effect, just in a different light.
There are other changes too btw:
> Keiichi was the one to explain Shion to Rena - he kind of covered for Mion as opposed to Mion having to explain herself.
> "Shion" told Keiichi to give the containers back to Mion, prompting Shion being brought up around the whole club (could have been clutch if Satoko mentioned something about her Nee-Nee) & the interaction with Rena where he definitely remembered something. This is a case where reordering the events caused a pretty noteworthy change in what happens, so keep looking out for these.
Lots more could have changed that we don't know yet, tho. We don't know if "Mion" & "Shion" are actually Mion & Shion yet. It could already be too late, or they simply could have already been switching out. We can't really be sure yet whether Keiichi actually gave the doll to Mion when he gave the doll to "Mion".
My only want from this arc is ''Mion'' to not go insane for the sake of making a difference. From my own research, According to Rika in WN, Mion has never went insane because of the syndrome EVEN ONCE Which speaks volumes about her incredible mental strength. I would be really sad If It gets ruined to make this arc different from the original, but since Mion got the doll, that should be near impossible anyway so It is fine I guess. I'm saying should cause of Keiichi running his mouth & saying shit to Rena in front of Mion "unlike Mion, Shion's really cute & has a nice smile!" might bring about the exact same thing but like two days delayed. But Mion's reactions to it confuse me as well.
One more thing btw, if you're usually like me & skip OPs & EDs, The end credits only list Mion & not Shion, which backs that up my theory of Mion playing pretend the whole episode.