Your original post insinuates that is is inherinately dangerous to shoot at "any hard flat surface" and you should "never" do it....
That would be incorrect and uniformed.
If what you ment to say is it "could be dangerous or even deadly" if done with damaged steel or improper ammunition / caliber than your absolutely correct.
I wouldn't be suprised by being struck with bullet fragments from steel, but it is very uncommon for someone to need stitches at a distance of 15 yards if they are using good steel and proper caliber ammunition
The Hunter Ed course is
basic. The subtleties of when a hard, flat surface is OK, and not, is not a "basic" concept.
In Basic Pistol the rule on a misfire is to keep the gun pointed in a safe direction for at least 30 seconds, in case it's a hangfire. If you're in an IDPA-type match and you get a click-no-bang, I'm guessing (from what IDPA types have told me, at least) that that's not the way it's done.
There is a difference between Basic information and what you can and cannot do, with an acceptable level of safety, when you have experience.
And as to whether the steel target is safe or not (note all the differing opinions in this thread about "safe" distance), you do have more chance of bounce-back from steel than from paper.
I'm not saying don't shoot steel. I don't, but if my kids wanted to at a match at my Club, I'd let them with proper eye protection, because, while kids, they're experienced enough to understand the small risk. And to suck up any ouchie that occurred.
All I'm saying is that having this happen should not come as a complete surprise. And, WRT the hunter part- the problem is that a ricochet means that you have no clue as to whether it's in a "safe" direction, regardless of where you were originally aiming.