Or even if there isn’t new physics for wireless transmission, it seems likely that a civilization living on a single planet would keep increasing the efficiency of their communications until very little radio leaks out.
Even further, advances in coding schemes make data look increasingly like noise to the outside observer. Think of the readability of a text file versus the same file after zip compression
or encryption
Like we have. Moved a lot from radio over to the internet. Highly focused communication.
Still that uses a lot of radio signals (Wi-Fi)
Good luck detecting a Wi-Fi access point from orbit, let alone the next starsystem over.