Steel capped boots can chop your toes off in an accident.
As with anything, there is no "easy answer or magic pill" that explains or does everything. While what you said may be true I don't think that's the whole story or even the most common result. In this case I think it depends on the type of accident and quality of the boot among other factors.
As I understand things, toe injuries due to steel toed boots are caused when your foot and toes (and the steel cap) are bent so far back that the top edge of the steel is now trying to touch the sole of your boot. Of course your toes are in the way. This is possible at high speed with boots that have flimsy, thin or otherwise weak and inadequate soles. Some better boots have stronger soles that would resist being bent back at that point. Better soles may also aid in preventing twisting and crushing from the side, if the bike falls on ones foot for example. They may be a little harder to walk in but they won't give way when you need them. Generally boots and high speed accidents are quite possible on a motorcycle.
When buying boots, try bending them back like that and twisting from the toe and heel. If you can bend and twist a lot and they are brand new, it's only going to be easier (worse) after wearing them for a while. At that point I'd say that things like steel caps, buckles, armor are more decorative fashion sound-bites than an overall safer boot.
So if an inexperienced or unskilled rider buys cheap boots (but "Steel Toed" sounds cool and bad-ass and, "They were only $30.00! YEAH!") and then rides faster than his skill level and whacks his foot on something at high speed, Yes it's possible that rider would experience foot and toe injuries.
And all of those points are quite common; Inexperienced rider, buying cheap gear, riding faster than he knows how to, and crashing. Happens all the time.
I think steel toed boots were originally designed for work in factories where crushing was a possibility. Good quality steel toed boots will generally withstand crushing forces when applied from the top.
Which is exactly what happened to me.
That morning I decided to wear the steel toed boots. When the SUV got to the steel cap, it immediately supported the weight of the small truck and nothing happened. I was still trapped but not crushed. They drove off and then I continued home. All I had later was a little redness at the initial pinch on the side of my foot. No pain or damage at all. I was very happy I decided to wear those boots rather than the lighter Doc Martens.
Just my experience and opinion of course.