My miltary experience is limited to the six years I spent in the USN. So take this with that in mind.
It was my experience that when it came to equipment design and service members, the designer would try to idiot proof the equiment because when you work towards the lowest common denominator that will be using the equipment, that's pretty far down the intelligence chain.
So when I read that the grenade had an adjustable setting that any infantryman could adjust the BS meter in my head went off. I know we could set timed fuses on our 5 inch rounds and I'm positive that holds true for the Army's artillery but for a grenade to be adjustable sounds wrong.
I could be wrong and if I am it wouldn't be the first time.
So when I read that the grenade had an adjustable setting that any infantryman could adjust the BS meter in my head went off. Not sure where you read that. I can't remember any hand grenade that had an adjustable timer as you describe.
The way it was done, is you "assumed" a 3-5 second minimum delay before it went bang!
I was taught how to cook off a grenade prior to throwing it. Basically, pull the pin, let the spoon release, count, then toss.
Another method I've heard about is to have your buddy pull the pin and release the spoon, toss the grenade to you, then you throw. Never tried that.