Every question here can be answered by the simple reality: Kaido never claims this as his "Top 5™" and never definitively declares the characters he imagined to be an exhaustive list of the only individuals he views as capable of giving him a fight. They were simply the most thematically relevant and meaningfully comparable to Luffy in his minds eye.
Oda already clearly laid out that Big Mom and Kaido had general parity when he had them fight for multiple days in a pure stalemate, with Big Mom effectively being more nerfed the whole time, even. This is something he only ever does for people he blatantly intends for readers to understand as being roughly neck-and-neck in strength, and no amount of quibbling/nitpicking over how it doesn't scale to their peaks—which, yeah, it doesn't scale to either of their peaks, since both can go unquantifiably higher and never faced off with those subsequent powerups to prove a different basis for their comparison—subtracts from that fundamental authorial intention of showing their equal stalemate as a substantiation of their comparable threats. So he never even had a reason to include her in that vision, which is entirely obvious to anyone who can actually read, since she was literally already proven to qualify by direct showings.
Powerscalers, as per the usual, just made up a whole different version of what Kaido's "Mt. Rushmore" was and idiotically ran with it for years while perpetuating completely fabricated reasonings for how it applies to the rest of the setting. As appropriately disappointing as you'd expect of powerscalers, really.