You'll see the reference to “telecommunications” there, because the offence you're talking about, which is now found in clause 15, was originally in the predecessor to Bill C-51; it was in Bill C-46. So for consistency purposes, this is using the same language.
The intention here, though, in replacing “computer system” with “telecommunication” is to use the term that is the broadest term to capture all kinds of technology that will fit under it. It's not just a computer system, for example, on your desktop; it may be your iPhone that has a computer system, a telecommunication system.