Haven't testing rates increased significantly? A natural outcome would be that we see more mild cases which previously would have flown under the radar.

I don't buy the article's hypothesis of social distancing being a factor. Social distancing has been ongoing for a long time, and if anything it's happening less now as people fear the virus less with dropping fatalities. So why would social distancing suddenly now begin to have a greater effect?

Mask usage could play a role. If you're infected while wearing a mask your initial viral load is likely significantly reduced. And at least here in England masks were not mandatory until recently.