If I remember correctly, they only refilled the shop because they weren't able to launch the next event on schedule and thus had to prolong the current event. And as retribution, they refilled the shop.
But although it's not the norm, it's not bad to prepare for it as long as it doesn't take much time. After all, the only thing that's consistent about nutaku is the certainty that something will go awry once every 2-3 maintenances^^