He has to use a different method because obviously he does not have a backdoor into the prime minister's phone. The fact that "obviously wrong" invasive methods have to be used (now) to imitate something that the prime minister want to apply to every citizen (except himself and his buddies) in the future can be seen as part of the point.

It’s not fundamentally different than indiscriminately scanning everyone’s private communication (what the Danish government is trying to accomplish on the EU level)

It's not that complicated. Minister wants to remove citizens privacy. Protester invades privacy of minister in response. On the one hand I agree that gps-tracking is not exactly the same as analyzing people's messages, on the other hand one can often infer whereabouts through messaging services indirectly or even directly such as when people share their gps location with one another (a feature that e.g. whatsapp has).

Anyway, apparently this Peter Hummelgaard has said:

"I indisputably believe that surveillance creates an increased sense of security ... and given that the prerequisite for freedom is security, yes, I believe that more surveillance equates to more freedom"

so I think you will find it easier to understand these kinds of protest actions if you consider them in the context of privacy vs. surveillance more broadly conceived.

(source for quote https://mastodon.social/@chatcontrol/115314954743042414 -> https://www.dr.dk/lyd/special-radio/prompt/prompt-2025/egois...)