I actually see this happen to a lot of guys too. Proper shooting stance will take a lot of the kick out of it however. Whenever I take someone new to shooting to the range I always let them fire off a few rounds from my Mossberg 590 just to see the look on their faces afterwards. The slow motion actually puts a lot of perspective on how powerful shotguns really are.
Gotta love the fact that each one of those ladies came away with a smile on their face despite the new bruise forming on their shoulder.
Not ashamed to admit that this happened to me with the first pull of the trigger as well. I thought I knew how to seat the gun properly, and I thought I knew what the recoil was like from firing handguns and rifles. Yeah, right!
In any case I got it right afterwards.
What I find annoying is when people will stand straight up and down and shoot; then, instead of changing their grip and stance once the gun recoils nearly 90 degrees, they wait until the muzzle is back on target and DO IT AGAIN.
One of the biggest problems these ladies faced was improper fit on the gun. If they could get the proper length of pull, they would be far more able to get into the proper stance that you wrote about, and undoubtedly would find the experience much more pleasant altogether.