Earlier quoted context omitted.
That's kinda the point. We define what a spherical cow is to be able to compare the real world against it. The problem for economists is that lay persons take that spherical cow to be truth and base whole ideological systems on those spherical cow.
Economists take the spherical cow as, if not the current state of cow-dom, the perfected nature of cows and what cows would be if they got to make the rules.
The almost purely "logical" and "ideological" statements of 19th and early-to-mid 20th century economics have been supplanted with with more empirical methods.