I read that too but actually the case augmentation is not statistically significant yet (comparing d1 and d2 after the reopening is not enough). You'll have to wait until at least d4 to have a better idea and i think they can manage to wait until week two to decide to either go for herd immunity (at R0 ~ 1 this is viable, deadly but viable for healthcare workers) or lock their country for a month again.
I doubt that you can measure this already, it has only been two days (also when the lockdown started it took over a week until the effect was visible). That's why at least some countries want to take it slow, after each small step you need at least two weeks to judge the effects.