I've read some of the latest research on transmission recently and it's very focused on surfaces and indoors. Yes, one could get the virus by being directly coughed on or spat at (in any setting), but the risk revolves around surfaces on which these aerosols settle, because the virus survives for days on end. Even indoors, it might take up to fifteen minutes of close proximity to get a 'viral load' (in the absence of projectile snot)
So catching it in passing outdoors is not the transmission vehicle of concern, although the Govt. use the blanket 2m rule cos its simple
'Covid-virology according to Big Cat'
(taking no responsibility for anyone getting ill!)