The reverse voltage breakdown being 2X the supply voltage is a safety factor.
The forward current rating of a rectifier type diode , say a 1N4001 is continuous 1A Average, but it is rated for 30A for one 60Hz Half-Cycle (8.33mS), or is rated for a Peak Forward Surge Current of 14A lasting 20 Half-cycles (166ms), which would be an average current of ~5A.
When you connect a snubber (catch) diode around a relay or solenoid, how long does it take for the current to decay? Most inductive loads I have measured have a decay time-constant of less than 100ms. Even though the 1N4001 data sheet doesn't have a graph specifically for Snubber rating, the graph below suggests that a 1A diode will suppress an inductive load carrying 5A just before being turned off. I have done it routinely, and not had any problems...