This is a very useful saying and reminds us all that we can very rarely look at the reduced-form equation. We need to look at the whole system of equations. Scott Sumner discusses some other things we shouldn’t reason from here.
Among my favorites:
6. Never reason from an aggregate wage change: (Yes wages are a price, but I haven’t discussed this one yet.) Higher real wages could be healthy, reflecting faster productivity growth. Or they could be unhealthy, reflecting deflation and sticky nominal wages.