I read the study that the 24 day timeline comes from - it's a rather uncertain worst case scenario. IIRC it comes from a single case report and it's more likely there's a gap in the transmission path that makes the incubation period look longer than it is.

A more recent study from Chinese researchers (so I don't know how much it can be trusted) studied 1099 infections and reported a more reassuring mean incubation period of 3 days.