From what I’ve read here and there, the max incubation before symptoms is about 14 days with the average at about 5. Could be more or less. And I’d take the word about transmission before symptoms with a grain of salt, although it’s possible with other viruses, too. Maybe they’re referring to communication before pneumonia (very possible) instead of communication before fever (less likely).
[Disclaimer: I was a poor intro. biology student and developed an interest years afterwards.]
Something that comes to my mind is that “normal” temperature for any given individual varies with the individual: It can be as low as 97 deg. F. My Mom normally runs about 97.5 deg F.
Can a person with a mild case 2019-nCoV have a temperature 1.5 deg. F above their “normal” temperature, with no other significant / visible symptoms, and be at least somewhat contagious? IF yes, I think it’s easy to see where this goes...