Good catch. So in a sense this isn't really Hyrum's Law (which would be more appropriate to things like the Sim City / Windows 3.x UAF bug described in a sibling comment); it's more like, if people need to do something, and you don't give people an explicit way to do it, they'll find an implicit way, and then you're stuck supporting whatever that happened to be.

There was a well-known trick in MacOS development in the 90s. You couldn't always avoid relying on undocumented behavior. The docs were incomplete and occasionally vague.

What you could do was try to rely on the same undocumented behavior as everyone else. This way, if Apple broke you, they'd break half their ecosystem at the same time.