Physical Vs chemical changes.
It was typically taught that physical changes are differentiated from chemical changes because they could be "undone" or that they had "no chemical reaction." Which was very confusing, because you can't uncut paper, and dissolving stuff in water clearly results in different chemicals being produced, yet both were examples of physical changes (actually the latter is sometimes taught as a chemical change). Furthermore, most chemical changes are actually reversible.
It has since been recognised that this classification is BS, and most changes actually exist on a continuum.
Eww Reinhart and Rogoff, all my homies hate Reinhart and Rogoff.
TL:DR Reinhart and Rogoff infamously cherry picked their data and had coding errors to support austerity measures that fucked over much of the world, subsequent meta analyses found that austerity doesn't work.
Growth in a Time of Debt - Wikipedia - https://en.m.wikipedia.org/wiki/Growth_in_a_Time_of_Debt