They could always be better defined. I haven't put my mind to it, because in the one particular case, the Young case that you're discussing, it clearly is covered by subparagraph (i):
if the disclosure is essential in the public interest for purposes such as
(i) the investigation of a serious offence where—[the person]—has been involved in the commission of, the offence.
What more do you want?
The person allegedly has committed murder. It's being investigated by the police, and certainly the RCMP, if it's using him as an informant, would be investigating along with other police forces, and in that particular case it clearly is covered.
How the RCMP has said that anyone is wrong when they say that the RCMP should be able to disclose that, is beyond me. I think it's disclosure 101.