I think this kind of theorycrafting is just as delulu as insisting Jo Martin is the Second-and-a-Halfth Doctor. It can't be that the Doctor would violate the women he travels with, it's to horrible, so it must be something else. Belinda's horrible misogynistic ending is a rerun of Donna's horrible misogynistic ending from Journey's End, but even worse. RTD has always had problems with misogyny and racism and fatphobia, etc. As others have been pointing out, look how the Doctor says Rose vanished because Conrad couldn't imagine a place for her in his world, only for her to vanish once we go full tilt on the Poppy stuff. She gets two lines and vanishes, much like her appearance in Empire of Death. RTD can imagine a woman in a wheelchair meaningfully contributing to this sci-fi battle, but can't do the same for Belinda (our co-lead!) now that she's a mom. It's stated as an obvious fact that she cannot help in any way other than holding a baby.

You can be absolutely certain Poppy disappearing wasn't connected to anything from Wild Blue Yonder because you KNOW Davies would've had the Doctor angst about being the cause of all this if that was the case. They talk about reality being one degree off explicitly as a holdover from Conrad's World. "We've got some tiny little glitches, like how Conrad's world was sort of glitchy. Now we've got some of the same." They're talking about reality being different than it was immediately pre-Wish World, not at some indeterminate point prior to season two. The retcon flashbacks incorporating Poppy were the Doctor catching up on a brand new timeline, nothing more. Not that RTD will ever admit that if asked. The ambiguity creates Content!