If you swop 'symptomless 'for 'asymptomatic' perhaps the familiarity of this concept throughout the pandemic will be a little more apparent
And yes, regular testing to show asymptomatic or pre-symptomatic infection has been with us for about a year now.
It's really not news.
A dead host is a dead end true, but not really relevant to covid, which spreads before the onset of symptoms (assuming there symptoms) so it doesn't matter how quickly it kills that host as it's already moved on