I think that's why this sort of phrase never made much sense to me, because in the same sense that the broken clock is right, a working clock with an offset (technically all of them) is almost never right (as you mention). Maybe it extends the metaphor, though, because while the working clock is never completely accurate, it's much more useful by being closer to the truth the vast majority of the time.

A broken clock running 6x its speed will also be correct much more often than a stopped clock.