For any rocket, especially using motor ejection, ideally you want the ejection charge to fire near apogee as it’s going the slowest around then. If the ejection charge goes off on the up boost, then that could result in a zipper to the airframe. (A zipper is when the shock cord cuts through the airframe due to ejection occurring when the rocket is still going fast.) If the ejection charge goes off on the way down, then that too could zipper the airframe. Or in either case, the shock cord could break resulting in the rocket coming down unsafely and crashing. So like Goldilocks, you want it just right. Depends on the weight, size and drag of the rocket. For a larger, heavier rocket, 6 secs could be too long. For a small light rocket, 6 secs could be too short. The size of the motor along with the delay need to be considered for the rocket.
