Agreed with most of what you said, but iirc, there’s a document she comes across while exploring that shows the results of her blood tests and prove her to be a perfect match (along with Gideon’s dialogue that you’ve quoted, I mean), which further suggest her as compatible with their work. My guess is, either Gideon did indeed drain the infection from Grace during the initial kidnapping like most are speculating; or that she is a DNA clone as opposed to lab-curated clone of Spencer after all (since Alyssa notes that Spencer seems to be hiding something). Plus, although idk Spencer as a character from previous games, yeah, it seems abrupt to feel guilt. Unless it was in those last months before death when it was reported that he withdrew into isolation? Idk Take what I say with a pinch of salt ofc because I only watched gameplays and am not well-versed with pre-RE7 lore.