It’s not just that, although that’s certainly part of it. As such a famous “traitor” he was a target of the Stasi, and as people knew from the Gestapo, operations don’t necessarily seize just because the organization is officially shut down.

Now, all in all, he wasn’t very important and nobody actually came for him, however, thanks to the panoptic nature of the GDR surveillance state you never knew what exactly was important and what wasn’t, who watched or if you were watched. So associating with a traitor was dangerous.

That is the nature of mass surveillance. And also a reminder for today. The Stasi would’ve creamed itself if it had a quarter of the tools available today.