Intuitively I agree some kind of selective amplification should be able to correct for the mistakes. But I think it will be complicated. Because the filtering process needs to be much more complex. It can’t just chemically match to a known subsequence - you won’t know where the mistake might be in a long sequence.

This is a good point. WXYZ and WYXZ are indistinguishable via PCR. And the possibilities accumulate with more segments.