It would never occur to me to even think of this. I would have been hanging my washing out on a communal washline through out lockdown without a qualm were I in a block of flats.
The washing itself will have been through a thorough wash in the WM. You can always ramp the washing temperature up to 60 ifyou are worried and wipe the line with a wipe before hanging clothes out
After that, blowing in the fresh air, will kill any remaiinaning virus, unless you have a neighbours and childrenwho wrap themselves in the clothes or blow
their noses on them - and then, yes, you do have a problem, but not necessarily a COVID problm.