The CDC report seems to be talking about medical facilities caring for seriously ill patients rather than people out in the open air.
However, there does seem to be ambiguity about precisely what "airborne" means. This is only Wired so a journalistic summary of the arguement: [www.wired.com
"Notably, while the joint WHO-China mission report published in late-February said that although airborne particles were “not believed to be a major driver of transmission,” it noted that such a mode “can be envisaged if certain aerosol-generating procedures are conducted in health care facilities.”
Julian Tang and his colleagues have created a visualization of the breaths exchanged by two people in conversation standing three feet apart. Most of the time, the puffs of air they let out remain separate; but portions of their exhalations do sneak from each person’s breathing space into the other’s.
"Given all this uncertainty, some experts say there needs to be better public messaging on the spread of the new coronavirus. “Crowded public transport where people can breathe on each other may also lead to transmission of infection,” Tang says, echoing public-health advice that, while widespread, may not be getting as much emphasis as hand-washing. Milton agrees, adding that it might be wise to shut off air-recirculation systems in cars, which could potentially spread the pathogen among passengers."
I agree that the big crowds of cyclists on the superhighways queuing at the lights wouldn't fit a definition of "social distancing". The truth as always seems more nuanced than appears at first glance.