Why should Hiyori reveal that Hiyori is still alive? Especially while she let Orochi think that even her alter ego is dead.
Orochi wouldn't know the truth about Komurasaki being Hiyori...something which can be used against the cowardly n superstitious Orochi , especially if she were to reveal a cat or actual Nekomata devil fruit ( another theory for another day ), tricking him into believing she's an actual Yokai/evil spirit. I think she and Kyoshiro are plotting their own coup of sorts on the side, a plot which could ultimately see Kyoshiro and Hiyori gaining Kaido's favor by convincing Kaido's that Orochi's a fool whose ineptitude is to blame for the Alliance's success thus far.
Revealing herself could likewise help fuck over the Alliance, thereby killing two birds w/ one stone. I believe Hiyori may be holding a grudge against her brother and/or entire family and retainers....with the possible exception of some of the other Scabbards who may end up siding with her for various reasons, if not having helped her from the beginning ( Kiku, Kanjuro, a reluctant Kawamatsu? ). It's heavy Alliance in-fighting.
Couple that with some a/several traitorous Minks -- cause no race is perfect -- who likewise come to hate the Kozuki after learning some troubling facts or rumors about the Kozuki's true relationship with the Minks going back a century: subjugation at the hands of a past user of Tama's devil fruit ability.
It's Civil War everywhere amongst all the factions; a huge theme that'll echo throughout the arc. Betting the Rocks' downfall will be revealed to have been partly caused by Xebec's crew bailing on him....the seeds for inner turmoil plaguing the Marines have been planted with the reveal of SWORD and what they learned about the WG's dealings w/ Kaido...we may even see some betrayals occurring in Big Mom's camp.
Mostly just speculation and gut feelings on my part.
