Re status of the NNU - it had designated ICU cots, in nursery 1, requiring one-to-one nursing, HD (high dependency) cots in nursery 2, and SC (special care) cots in nurseries 3 and 4.
So you you wouldn't call the whole unit a NICU and you would expect children in different nurseries to have more or less acute needs. But they also moved between nurseries, in both directions, as their conditions fluctuated. They were supposed to be transferred to level 3 facilities if on ventilation for more than a certain amount of time (I think 24 or 48 hours), if they needed surgery, if they were below a certain weight, or if they were born below a certain gestation, though in practice this wasn't strictly observed.
For the babies Lucy Letby was accused of killing, babies, A, C, D, and E were in nursery 1 from birth.
Baby I was moved between nurseries and hospitals, but was on nursery 1 for the shift when she died. Babies O and P were supposed to have one-to-one nursing but instead were placed in nursery 2 with a 1:3 ratio. Baby O was transferred to nursery 1 after an initial collapse, but there was no room in nursery 1 to do the same for baby P the next morning.
The babies she was accused of harming but not killing:
child B, child F, child H, child K, child L, child M, child N (one event) and child Q were in nursery 1 (ICU).
Child G, child J were in nursery 2, high dependency. (Child G vomited and deteriorated after this, with a documented infection, and Lucy Letby wasn't found guilty of harming child J).
Child N was in nursery 3, expected to go home that day, when he deteriorated from before Lucy Letby's shift. Again, she was found not guilty of that attack, presumably because it was so obvious she wasn't there.
So, while you can say that the NNU had cots for children who were recovering, feeding and growing, this doesn't mean it didn't provide ICU care (until it was downgraded). None of the children Lucy Letby was accused of killing came into this recovering, feeding and growing category. A small number of her "attacks" are meant to have happened outside the ICU cots. Children in rooms 2, 3 and 4 could and did deteriorate, but these events were very much the exception in the charges against Lucy Letby.