It is not so much that the court says it is suspected of terrorism as that the agency responsible for monitoring that says so and the AfD tried to use the court to get rid of that label and failed.

Not to worry intelligence services and police already were monitoring the communications and even infiltrated left-wing extremist groups like Last Generation known terrorists that do extreme things like marches and protests.

Like you already know this but the germans were already doing this against left wing groups. This isn't because germans have a problem with Nazis it's because AfD is soft on Russia and China like they've been Nazis for as long as they've been around but it's only recently become a problem so now they acknowledge something everyone knew for literal decades.