What makes you think they have to prove detriment? Section 359B(d)(ii) is an 'or' clause, not an 'and' clause, as is the s359A list, which is an 'includes' list, not an 'is' list, which means it's non-exhaustive, and it's s 359E that makes unlawful stalking a crime, not s 359B, so 359E is what you are being charged under. It doesn't matter which descriptor in s 359B your action falls under; if your action meets any one of those descriptors in s 359B, you're guilty of a crime under s 359E.
Why does the government provide such broad definitions? Because it doesn't allow people to get away with violating the rights of others because they violated them slightly differently to what is "allowed".