If a quote is incomplete and a meaningful part is omitted there are other typographical conventions to indicate that, like a double period .. for example
Yes, but what I'm talking about is the reverse situation. How would you know whether or not the quoting (outer) sentence is complete? You cannot logically infer that from the quoted (inner) sentence, which is why I'm saying that the second period is not redudant.
That is true for the inner sentence, but again, I'm talking about the outer sentence. It needs its own terminator to make it unambiguously clear that it is complete.