IMHO, the authors were trying for a more powerful Sudden Light and just made it a Sudden Light V with the 50' radius.
This would be where the Sudden Light goes on the List; Light Molding 4th lvl, Light Law 5th lvl, Light's Way 5th lvl.
But since it is Arcane, it is scaled up to a "V" and given 50' rad.
Just an opinion.