(I am a NICU data analyst)
It probably means that he is showing generalized signs of infection, but they have not isolated a specific bacteria. It could be anything from increased temp and respiratory rate to something “bigger” than that. I doubt they are sugar-coating it. NICU docs are typically very matter-of-fact (if he was septic and might die, they would have told that to the parents so that they could prepare themselves and the baby).
My friend had twins born at 24 weeks and at one point was told “your baby has E. coli growing in her blood. She is the sickest baby in the unit and might die.”
The only real issue with not isolating a specific bacteria in this case is that they cannot know for sure what antibiotics to use, so they will probably use a couple of antibiotics to cover a broad range.
This happens often in preemies. Please don’t take internet searches out of context. If he is critically ill, the doctors have an obligation to tell the parents.
I’m sorry for the parents/family. This is that roller-coaster that preemies ride for months.