Your rear hub might be good while the OP's might have been defective. Just like cranks from reputable brands break (even though, theoretically, no human can do that); there is always the possibility of a certain number of defective units. That doesn't make them defective by design, but by manufacturing. Presumably, reputable manufacturers such as Shimano, Sram or Sun would produce parts that are less likely to fail. Etc. (let's not get into this right now).

A loose cog pushing into the lockring is the most common/natural cause of stripped lockring threads. That may also be an indication of poor hub material quality. The easier an alloy is to machine, the less strong the threads will be - this is a simple rule of thumb, which leads to the reason why cheap hubs are more likely to be made of materials that aren't as strong as the ones of more expensive ones.

That said, from what I could see on the pictures posted by the OP, the threads weren't (only) sheared off, but the part itself was cracked/cleaved/broken off. So probably the threads weren't the weak point as much as the bulk of the material may have contained a defect.

Finally, to return to "operator error": I really don't expect the OP, or any rider, casual or not, to remove the lockring and the cog and rotafixa the cog back onto the hub. It's very reasonable to expect that at least that part is done well. But who knows, maybe the trend from now on should be to actually remove the cog from new wheelsets, apply Loctite to the cog's threads and rotafixa it back. Seems like a worthwhile initiative, perhaps? It's always better if the cog is kept in place by the cog threads, rather than testing the lockring threads with lateral force. Plus the hub body at the lockring is weaker than at the cog.