The regenerate functionality goes back many years in the history of the Maestro engine.  I wrote the very first instance of the "Maestro" engine back in 2004/2005 where it was nowhere near as flexible and nowhere near as extensible as it is today as Maestro.  That being said, the engine's internals have been updated and upgraded over the years which has culminated in what you see today.  The concept of regenerate and regenerate all live tasks comes from the very beginning of the engine's life and lives today in Maestro 1.0's engine.