Why does the published_at date sometimes precede the created_at date?

[waynebanksy]

I'm trying to analyze some data of different websites specifically to understand "launch_dates", which is another way of defining the "published_at" date for a specific product. For a small number of products from different websites, the published_at date is < the created_at date, which does not fit into the definition of the two data points as described in the API docs (https://shopify.dev/docs/api/liquid/objects/product). 

Can any one explain why data would present this way? And which data point (either published_at or created_at) would most closely represent the "launch_date" or the date that the product becomes available for sale on a brand's website in this unique situation where the published_at date is earlier than the created_at date?