I own a range, and I have a fair amount of different steel.
I have built hangers for some,, and I've also seen many others & ideas.
From what I see above,, here are a few thoughts.
The wood can & will be damaged & have to be replaced occasionally. Either bullet splatter or misses will cause this.
That target is a whole design in itself,, making you have to buy their system. Not adaptable to other types of targets.
The portion of the frame that holds the wood,, it can & will be hit sooner or later,, and can it be fixed, replaced or whatever? Judging by what I see,, not easily. If a bullet hits the edge of a wood brace,, it will warp & you may not be able to get the wood out,, or fix it easily.
I make metal frames,, and hang steel from heavy chains,, with screw links,, and I keep spare links to replace the ones that get damaged. I also have solid metal frames that hold a target at an angle, allowing the bullets to either pass most of the frame, or when they hit the target,, splatter towards the ground.
If you are considering steel for your practice,, look at the FACT it will get hit in places other than the plate. Can it withstand many impacts from whatever you are using?
Heavy chains,, quick links, heavy angle iron are all good materials to use to build frames. I have a plate rack I built,, and I used an old motor grader scrape blade as a bullet deflector to protect the frame where the plates sit. The harder the steel,, the better it withstands abuse.