At no point in the current expression you wrote "-", though. It may make sense that if you type [-] [2] [x^2] [=] then you get -(2²) = -4, but if your current answer is already -2, then tapping x² should result in (ans)^2 = (-2)^2 = 4. Splitting your current answer into a separate unary [-] as in - (2²) makes absolutely no sense.

Most calculators, even CAS ones, simply get this always right. But sadly this is not the first "desktop" calculator that I see getting this completely wrong. And it makes some results outright wrong!