I'll offer another opinion, just for variety.
The parts of that target that are still valid for two handed shooting are jerking the trigger (you'll shoot low/left), applying thumb pressure with your strong hand (you'll break right), too much trigger can go either way, left or right (if it's in the crease), too little trigger will push left (always). Flinching is a crap shoot on which way it goes.
Incorrect balance between strong and support hands will cause lots of problems, not all predictable. Generally speaking an incorrect hold will cause a lot of wobble in your sight picture and alignment, while a balanced, relaxed natural hold will reduce wobble.
Where it starts to get tricky, the larger the recoil impulse, the more firm you have to be with your grip to control recoil, but as you tighten your grip you REALLY have to concentrate on keeping the parts that are supposed to be relaxed,
relaxed, such as the thumb, and keeping neutral pressure where it should be.
Generally I see inexperienced shooters throw wide patterns out, from nervousness, incorrect hold, recoil anticipation, flinching, etc.
If shots are hitting everywhere, a target like I, you, and others have linked to will just confuse the living hell out of someone. They'll think they're doing EVERYTHING wrong. That'll destroy their confidence and that will hurt their shooting capabilities more than anything else you could say or do. Might even make them not come back.
Those targets are best for the EXPERIENCED shooter who is shooting small groups but throws an occasional flyer and can't find out why, *OR* a person putting a good tight group together with a handgun that is known to be dead on, but off center.
My FiveSeven is my benchmark, I *know* it is dead on. It also shoots wickedly tight groups. If I hand that firearm to someone and they put together a 10 shot group low left, or to the right, I can zero in on their problem in short order. If they put together a centered 10" group with it at 10 yards, then I know we need to back up and work on the fundamentals of how to hold it, breathe properly, relax what needs to be relaxed, and so on. (I can shoot 6" groups at 50 yards with that particular firearm all day long, if someone shoots it 10" at 10 yards, that's ... really bad.). If they are recoil sensitive I break out the Ruger Mk3 target, it is also very accurate.
It is MUCH more difficult to teach someone to shoot well, than people would realize, because the signs are oh-so-very-subtle, and you cannot FEEL what they are FEELING. You can observe and try to interpret, but it's really difficult to SEE if someone is tightening their thumb when they shouldn't, or pushing left with their trigger finger as they pull it back.
The best student is one that listens, and spends time self-analyzing what they are doing. I try to explain to people "I can show you the fundamentals and get you started, but I can't climb inside your head and do it for you."
The absolute best tool for learning trigger and hold control is dry fire exercises, as the person can SEE the sights move when the trigger breaks.
What you can't prepare for is how it will recoil.
I bought a new 44 mag and took it out tonight for the first time. I dry fired it a hundred or so times last night, thought "yeah, I got this."
Then, I damn near broke my support index finger on the back of the trigger guard the first shot I fired. My hold that I practiced when dry firing was nice and stable, perfect sight alignment, sights didn't budge the slightest when I'd pull the trigger. But the hold I practiced was 100% incorrect for a firearm that recoils like that one.
So I'm practicing a different hold tonight (the one I discovered today that does NOT damage ME), and I'm working on getting that sight to not move tonight.
Click. Cock. Click. Cock. Click. Cock. Click. Etc.