Those parts are bigger than the output. The highest force is applied to the output, not the ratcheting mechanism, because the output is of lesser diameter.
That's assuming that the fastener is the smallest element in the system, and things get worse very quickly when the fastener is substantially bigger than the drive. In my particular case, it was a 1/2" drive on an 18mm socket, and it was the drive that broke. The size of the ratchet head was about an inch, so I'm guessing the ratchet itself was also around 18mm. Ratchet survived, but was kinda useless without the drive, and it wasn't worth it to open the wrench up and replace it. :-)
Having said that, I hadn't thought about grossly oversized ratchets/drives in conjunction with small fasteners. If you're turning a 1/2" bolt using a Hulk-like plastic ratchet with a 1" drive, you will have a lot more mechanical advantage to work with.