I think the premise behind 'wood grenade' style wedges is flawed. The idea is that you stick it in the middle of a round and let it find the
easiest place to split the round. But already the middle is the
toughest place. A wedge should be placed close to the near edge the same as your axe blow would be placed (unless you relish broken hafts). And you should have predetermined what line you wish to split, it may be through the center or it may be to some other point like splitting 1/3 off the right side of the round. On large rounds it's sometimes helpful to take a weak side off first. Then pick you next line, which again may or may not be through the center of the round.
When you've resorted to wedges you're already dealing with a big tough piece of wood. At that point you're going to have to be mindful of how you split it. All the youtube wood grenade 'how-to' videos show guys splitting little straight-grained rounds that you could make minced meat out of with 5 pound axe. Of course the wedge will split those. A boys axe would split them.
I've found that after 1 or 2 wedge splits the rest of the work can usually be done with a heavy axe.
Examples of some wedge work. These are 36" rounds of black cottonwood with a twisted coarse intertwined grain. Axe or maul won't touch it. Note how I start with a pair of wedges close to the edge. Once it starts to pop open I drive a 3rd wedge in on the far side of the split.
You don't get nice straight splits out of this stuff. I try to plan my saw cuts through the largest branch crotches to make them easier to split.
After they split the intertwined grain still holds them together. I used that big wrecking bar to pry them open so I could cut those strings with an axe.
Dealing with a crotch. I split off the weak side first. Then I start 2 wedges on the near side wood directly centered on the crotch.
This was some gnarly stuff to split.
All split.