> Then again, I haven't methodically gone further into the rabbit hole and just try to see if I can notice a new device being powered up in a blind test.

There is a well known mechanism by which it might be possible for you to notice a new device being powered up: coil whine (https://en.wikipedia.org/wiki/Coil_whine). It was very common in the CRT era (some people could instantly tell whenever a television set was powered on), but still persists today (for instance, it's a known problem on some laptop models).