Cooling is exponential, so it is fast where it doesn't matter and slow exactly where it does — the last twenty degrees take longer than the first sixty. That is why the rule has two gates, not one: 135° to 70° in two hours, then 70° to 41° in four more. A batch that sails through the first gate can still fail the second while nobody is watching. Shallower pans raise k. Nothing else in this equation is yours to change.