Re the bold: actual physical care of a newborn requires more than the use of a couple of fingers. I dunno what kind of infants everyone had has exposure to, but the ones I know required constant care, dexterity, constant vigilance, and lots of movement - walking, endless rocking, changing not only endless diapers but full blowouts/clothes (while holding down your own vomit at times), getting them comfortable, interacting. Hell, getting a mobile going over a crib or handing them a toy in the bassinette/crib/stroller/seat. Throw in something as minor as reflux and you'll be cleaning yourself up constantly, too. (And ime, might not even be able to hold them cradled, but instead they have to be upright 99% of awake time). Nursing, pumping, cleaning pump accessories, warming bottles...and that's before you get to anything like pap and solids. And once you get to baby food, they're wearing it as much as eating it. Baths and constant housecleaning. Even minor medications require dexterity to open/dose. You can't even snap a onesie or adjust a baby's socks or hats with one pained hand and very limited ROM.
And all that is before 6 months and it starts crawling. At which point you couldn't even rescue it if it got its finger pinched or the safety gate fell over on it (to name 2 of a billion things). (Oh, no worries, she can handle it if the baby's safely in a playpen/pack & play? Sure - until it chokes on a cheerio and she can't even reach it, much less pick it up and dislodge the thing.)
She will never be able to care for a baby physically. She can never be alone with the child. She will never be the actual primary caretaker of her child.
It's not right or fair to grade on a curve when it's a matter of reality and experience for the actual baby.
(And yet despite all of the above, it takes nothing to accidentally or purposefully stop an infant's breath if it's reachable. The difference might be ability to stop quickly. So absolutely agree that PPD/psychosis, as well as regular old parental exhaustion and patience limits, should be high on the watch list for the grandparents and paid caretaker
...and that applies to watching out for Noah, too. New babies and their incessant needs and presence have a way of stressing castles built on sand, even when one person is not a total physical dependent and the other is not a barely-adult person with documented domestic violence, drug, judgment, and anger issues.)