Group chats are the problem, not Signal itself.
Privacy
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*for internal communication
The EU Commission is cracking down harder on digital espionage. It has instructed its highest-ranking officials to immediately dissolve a central Signal group for internal communication. According to Politico, department heads and their deputies are primarily affected by this measure. The order stems from fears that the chat group may have become the target of targeted cyberattacks.
I assume it is to prevent this mess
https://en.wikipedia.org/wiki/United_States_government_group_chat_leaks
The article did reference the Signal chat leak. It's also worth noting that Signal is secure, its just also available to the public and not designed for officials only. Cryptography is useless if the device itself is compromised or if someone is added to a chat. I assume they're making people use an internal system that only officials have accounts on. That way you can accidentally add a journalist or impersonator to the chat.
While Signal is still considered one of the most secure options, security ends when the end device itself is compromised. If an attacker gains control of the smartphone, even the best end-to-end encryption is of little use: chats and images can then be read directly on the device. However, Herpig emphasizes that there are currently few better alternatives to encrypted messengers like Signal or Threema.