Disney Springs is mostly 3rd party vendors who wouldn’t be happy to restrict non-resort customers. The only way that would work is to lock it down at the entrance points from the garages and test everyone as they enter. This way if a resort guest takes the Disney bus to DS they never leave the bubble. Anyone driving and parking would have to be tested again.
They'd also probably start enforcing WDW Transportation for on property guests only. Which they could do via MB. Would cost a bit to equip every bus and/or bus stop (considering they'd now have to be manned) with MB readers. I suppose they could start only with the DS depot. Same would have to be true for the boats servicing the DS resorts.