Comment by kibwen

> This effect serves to constrain changes to the implementation, which must now conform to both the explicitly documented interface, as well as the implicit interface captured by usage.

Let's be clear that this is one interpretation of the phenomenon described here, which we might call "The Doomerist Interpretation of Hyrum's Law". For everyone else, the whole reason that we bother categorize interface details into "public" and "private" buckets is precisely so we have the moral high ground to to tell people to go kick rocks when they get they get uppity about their own failure to adhere to the publicly documented interface.