[abecedarius]

As therajiv pointed out, there were only a handful of data points supporting the kink in the curve, down at its end, versus lots and lots for the main line. Even in freshman physics labs you get told it's a terrible idea to extrapolate from a few points at the end of a curve, because those are typically the noisiest.

[tedsanders]

Certainly. But the issues of a linear model being "correct" and how to extrapolate forward are not the same.