This difference could not exist at all or vary depending on which personal project or production app you're talking about. However, I think that because personal projects generally have solo developers and are more about single use or fast shipping, they tend to have less tests, less of a focus on architecture and modularity, and less documentation.
Those seem like pretty easy hurdles to get across if you've never created or been on a team that creates large-scale production applications. Why is the distinction so prevalent on job postings?