On this as an ex soldier I have to disagree.
A grenade is designed that if it falls and lands on a hard service it will not go off. Unless the pin is pulled by roughly two pounds of pressure releasing the handle which then causes a reaction that after 30 seconds will cause the grenade to explode. Those 30 seconds gives the person pulling the pin enough time to throw it. See the pic below.
As to rigging it that's relevantly easy also you just take a small thin metal wire, connect it to the grenade, and place the grenade and wire, the wire pulled very tight, at roughly ankle lvl. Low enough not to be readily seen yet high enough to cause the person tripping the wire to pull the pin with his body weight. 30 seconds later, boom. In this regard per my post the metal wire had yet to be attached to the pin so in Reality the grenades would not have fallen far enough or had their pins pulled. Plus they were low enough that the impact from dropping would have not been very much.
As for facing you just place the fat part opposite the pin and handle facing the general direction you want the blast to go. With a flash bang it explodes like a fireball in all directions so facing is not a problem. I seen kids do it better then some career soldiers. It’s not that hard.
Ok enough said lets move on. I'll try to get a post up by Sat once again but I have a lot going on so I maybe late so don't hate me if I am.