For a long time, Wizards of the Coast has maintained a "comprehensive rules" document that tries to be the canonical source for how everything works. In the past few years, they've been maintaining it less and less rigorously. An increasing share of their profit is coming from Arena, and as a company they're focusing on Arena quite a lot. Recently they added some Arena-only mechanics, and they didn't even bother putting those mechanics into the CR.

This market resolves to YES if a some point the Comprehensive Rules cease being "official", and we're instead supposed to defer to Arena if there's a disagreement between how the CR says something works and how it works on Arena.