Wickham doesn’t say to be “skeptical about the default position”, which implies being skeptical of the status quo. He seems to be saying be skeptical of what the data purports to be, until you understand its origin and collection process and etc.:

> But until you’ve understood the process by which the data has been collected and gathered ... I think you should be very skeptical. Your default position should be skepticism.

This seems reasonable to me. Data is inherently a simplification of the reality it purports to observe and store. Not adequately researching and challenging the data is taking too much of a leap and faith.