That was made after a liquid lunch.
Many years ago when was in basic training, had to toss grenades that were supposed to have a four second cook time. Sargents told us to keep in mind that some of them were made on Friday afternoons after liquid lunches in anticipation of liquid weekends, and some were made on Monday mornings with hang overs after liquid weekends. Don't count on four second cook offs because might be ten seconds where you and the enemy could throw them back and forth a few times, or might be 1/2 second where the enemy is glad never made it out of your hand, so pull the pin and throw it.
My advice? Pull the wire, yell fire in the hole, and throw it fast and far before it goes off when least expected. Just a suggestion is all.