Reasoning

The receiver of the surveillance runic armaments was no other than Felicia, the winged woman Nial had encountered in the cathedral of the Golden City upon arrival, and Siegfried.

Nial couldn't be sure that Felicia, as a fellow Balgris, would expose the secrets of her race's Prince, but he was not ready to trust Siegfried with his life.

Thus, Nial ended up adding all the contact details of the messenger crystals he had gotten to know into the receiver of the surveillance runic armament.

Finn didn't know that Nial had only a few contacts and that he didn't know the higher authorities' contact details. Nial took advantage of Finn's ignorance, which seemed to work perfectly fine.

Finn was not sure who Nial sent the livestream of the surveillance runic armament which was why he wanted to destroy it to prevent anyone from finding out more.