My understanding is that while the sources were left anonymous, they were definitely confirmed as intelligence agents by Bloomberg... so if they were duped, it's a pretty serious (propaganda-level?) duping.
This is where Bloomberg is already caught playing little loose with the truth. They are saying they have 17 sources, some of which are intelligence officials, but that doesn't mean they have 17 people confirming the specifics of these incidents. Apple's response notes that the accusation is reliant on a /single/ anonymous source. Intelligence officials may have simply confirmed that China is interested and tried to do this kind of thing.
As Greenwald pointed out years ago, it's sensible for readers to ask why sources are anonymous.
If they're saying something inconvenient to their government or employer, that's neutral or even positive for their credibility. If they're saying something convenient but classified or otherwise not-for-release, that's generally neutral; 'authorized leaking' is an established practice. But if they're saying something that won't cause them problems and isn't a secret, then it's strange. It raises the possibility that they're anonymous because the claim isn't true and they don't want to be embarrassed, or even that the story writer encouraged anonymity to hide the weakness of the source.
If Bloomberg is saying "we used 17 sources including intelligence officials and an anonymous source who confirmed the hack", well, easy money says the key anonymous source doesn't measure up to the other 16.