28 Days was shot with that video camera, and 28 Weeks was shot on super 16mm. (Neither of them had the camera written into the script, cloverfield/blair-witch style.) A newish iPhone can solidly outperform either of those cameras, even handheld without accessories. So I'd honestly worry that the film might look too good, and need to be degraded to match the aesthetic set by the previous films.
Whatever. The creators either know what they are doing, or they don't. But I'm still baffled as to why Apple doesn't take the simple and obvious step of adding bigger class and a camcorder form factor. The iPhone already does so much that "pro" cameras struggle with.
No it really can't outperform those cameras. The lenses on the iPhone are terrible. Sure the cameras are 48MP and can shoot 4k 30fps log which is great sounding but the glass in front of them is crap.
From a photography perspective, a 48MP iPhone 15 Pro Max can't touch a decade old entry level DSLR.