So a 100 year ship to Alpha Centauri requires a top speed of 0.08c. 0.08c is within the reach of the giant version of Orion. Snake oil defies natural law. Orion defies SPACE treaty only. Your assertion is without merit.
If it happens once, it's a bug. If it happens twice, it's a feature. If it happens more than twice, it's a design philosophy.