The main complaint and law that HateAid, the organization that lodged the complaint, is using, is that recording devices have to be visible as such. Glasses are not a known and widely accepted video/photo device and therefore affected by that law.
Effectively, their complaint is that a specific model looks too much like normal sunglasses that other people are unable to distinguish them as such.
Article with a bit more detail:
https://www.heise.de/en/news/AI-glasses-Criminal-charges-aga...
I imagine Meta and folks wearing these glasses would object to webcam like behavior where it tells you with a LED that it's consuming the video feed. Could be same for taking a picture.
But then probably fewer people would buy them.