I wonder if the graphs are affected by a "starting" bias, meaning is the mobility on the first date, February 17th for the charts I was looking at, used as the measure for seeing the trend on subsequent dates. The issue what if that date was particularly cold or rainy and then as we moved into March the weather got better of course you would see greater mobility movement as compared to a cold February day esp. the category of Parks and recreation
But instead had they used is sliding window for the baseline (i.e. using the average of the mobility for the past 3 years) for any given day then seeing what this year's date is as compared to that we would see (hopefully) a dramatic decline.
Just thinking out loud
Take care and STAY DISTANT