You're right that "wipeouts" and "total population turnover" basically doesn't exist in our genetic history, but there's one critical exception to that rule of thumb: massive epidemics really do wipe out entire local populations, and given that early farming was involved (with its higher pathogen burden) this cannot be ignored as a factor here.

We can’t say for certain what the causes were, but there are some very striking near-total population replacements we can infer from DNA analysis, such as the disappearance of Neolithic ancestry in Britain over the span of just a century or two.

Phys.org is good for DOI links to the studies they butcher and nothing else. It makes me cringe every time I see people discussing their writing seriously, but my God they’re a popular domain.

They’re often sensational and frequently inaccurate or misleading, but often the research they cite is worthwhile.