I've rigged up a system to force carbonate mini-kegs and they take 40 lbs of pressure with no problem, so I don't think their ability to withstand the pressure is the issue.
On the one or two kegs that popped out into pointy kegs when primed with sugar, the beer was wildly over-carbonated. Wildly. It's the once instance where I came close to injury in home brewing.
I've heard the same advice to "under prime" corny kegs, so I have to think there are other reasons. But I don't know what those reasons might be.
It's easy enough for someone who wants to prime their kegs to do a side by side experiment.