You keep ignoring the fact that that's false.
A person has sufficient viral community in them to spill over into saliva and contaminate towels, doorknobs, sheets, clothing, etc. where it can remain for hours and can be picked up and transmitted to another person, or sufficient to directly contaminate someone with whom they have bodily contact, especially males with the disease in whom the virus survives well in semen, .. for close to around 24 hours prior to the person with the virus being cognizant that they're experiencing symptoms.
You're simply mimicking the CDC line, and although that's sufficient for general communication to the public of demarcations necessary to present a concept to the lower common denominator public consistently, it simply isn't the truth.
The truth here is as I stated it, and that's a truth relevant to many viruses as they grow in numbers in a body, such as the common cold and the flu.
Indeed, the most dangerous time of contagion is right before one starts to "feel" sick, as it is during that final 24 hours of "incubation" when the viral community is beginning to spill over into saliva and other mucous when a person doesn't yet experience the symptoms that they will go about their business as usual, going to school, work, church, etc., completely oblivious to the fact that they've begun to leave a trail of virus on things they touch that can be picked up by others.
It's not about the carrier "showing" symptoms, as that's a calibration from a hypothetical healthcare provider "observing" a person with the virus and declaring "you've got symptoms".
Prior to such hypothetical observation, the person with the virus spilling out into saliva and other bodily fluids didn't feel sick so he didn't avail himself to this hypothetical healthcare provider for observation.
If he doesn't feel sick, he's not presenting sufficient symptoms to even himself to "show" symptoms.
So for that most dangerous 24 hours, those roughly 24 hours prior to sneezing, prior to stomach upset and diarrhea, prior to fever, prior to body aches, he's reached the "overflow" saturation point where he's spilling virus into his external environment.
It's easy to buy the CDC's "don't panic" line, partially because it presents a scenario whereby we can "feel" like we know when we're safe, and partially because it just sounds good.
But, it's false.
And the degree to which it is false is measured in hours, hours that provide a very dangerous window of contamination that those professionals who must monitor people to prevent an epidemic are most assuredly cognizant of, and will thus respect if they're competent professionals and have not been corrupted by agency politicizing to justify policy.