So why aren't the bolt "loops" made to be (bolt diameter + 50%) in
size, to allow for misalignment?

Because it's cheaper to cut them from the same piece of profile.

And the people who design/make/import/wholesale/retail them don't give a
toss about the poor buggers who install them. The list is endless.

If you have loose ones they rattle like hell on your bog door.

That's true enough - I hadn't thought of that detractor.

In that case, I think I'd like to see the bolt shaft either made oval at the
mating end, or have an offset - so when you push the bolt home into an
oversized "loop" the bolt goes in easily, then when you rotate the bolt
through 90 degrees, the mating end tightens in the loop in order to engage
snugly.